Case No. 245·United States
1964·Cisco Grove, Tahoe National Forest, California
United States.Cisco Grove · California
On the night of 4 September 1964, bow hunter Donald Shrum, separated from his group at Cisco Grove (California), climbed a tree and said he was besieged for hours by two humanoid beings and a red-eyed 'robot' that exhaled a vapor that knocked him unconscious. He defended himself with arrows and fire. A lost companion saw the same object; the case was investigated by Project Blue Book.
Year
1964
Tier
B
Probability
30%
Category
Incident
Limited evidence: single-witness, local or without primary verification. Three independent axes: the «tier» measures the strength of the evidence; the «probability» estimates how genuinely unexplained the case is —a natural phenomenon can remain unexplained, so it does not equal «non-prosaic»—; and the partition of explanations (below) says what it most plausibly was. So a well-documented case can have a possible hoax as its most plausible cause, and a Tier B is not, for that reason, a hoax.
Primary documents · viewer

Context · Tahoe National Forest (California), the Cisco Grove area
Nevada - Tahoe National Forest, California - NARA - 543569.jpg · Wikimedia Commons · Dominio público · open original
Part 01
The night in question
On 4 September 1964, 28-year-old Donald Shrum was bow-hunting with friends at Cisco Grove, in Tahoe National Forest (California). Separated from the group as night fell, he decided to climb a tree to spend the night safely. From there he saw a white light moving in a zigzag among the trees at low altitude; at first he thought it was a helicopter and climbed down to light flares to signal his position. The light turned toward him, stopped about fifty metres away and, as it settled, Shrum realized it was no known aircraft: he described a large, elongated object.
What followed is one of the strangest close encounters of the 'third kind' in the Project Blue Book file. According to Shrum, three figures approached the tree: two humanoids a little over five feet tall, with a silvery uniform covering their heads, and a third robotic-looking being, darker, with two reddish-orange eyes and a slit-like opening in place of a mouth that opened 'like an oven door'. The entities tried to dislodge him by shaking the tree. When a whitish vapor came from the 'robot', Shrum lost consciousness on at least one occasion. Terrified, he defended himself for hours: he threw burning bits of clothing and matches, which momentarily drove the beings back, and even shot arrows at the robot; on impact, a spark flew, which to him confirmed its metallic nature. When he last awoke, the beings were gone and he hung from the tree held only by his belt.
He was rescued by his companions, one of whom, Vincent Alvarez, had also become lost that night and said he had seen the same luminous object, corroborating at least that part of the account. Shrum took the case to the Air Force; Project Blue Book investigated it and, lacking a convincing explanation for the whole, tended to catalog it dismissively —it was even suggested he had mistaken hikers or structures for the 'beings'— a disposition civilian investigators considered unsatisfactory given the consistency and detail of the testimony over the years.
Part 02
Why this case moved the needle
Cisco Grove matters to the corpus as one of the most detailed close encounters of the third kind and, at once, as a test case for the limits of single-witness testimony. Its interest lies in an unusual combination of elements: a witness who held a coherent account for decades, a physical-effect component (loss of consciousness from the 'vapor', connecting to pattern 8a), an active defense with arrows and fire that would leave traces, and partial, independent corroboration —Vincent Alvarez saw the same luminous object. Few contact cases combine that degree of narrative concreteness with a second witness, even if only of the aerial phenomenon and not the beings.
Even so, analytical honesty splits the posterior between indeterminacy and the mundane/misid narrative, without loading onto the non-human. The core problem is structural: the extraordinary part of the account —humanoids, a gas-exhaling robot, an hours-long siege— rests entirely on one witness, in the dead of night, in a forest, under extreme fear and sleep deprivation, conditions that favor both the misperception of hikers, animals or structures and the later elaboration of a real but ambiguous experience; Blue Book's dismissive disposition points that way. Alvarez's corroboration reinforces that something luminous was in the sky, but does not validate the 'beings'. The mass left to the non-human open is real but modest, conditional on the physical details (the spark when the arrow hit, the vapor) being what the witness believed. In the corpus, Cisco Grove is the case that marks where narrative detail, however vivid and sustained, does not by itself suffice to move the probability: the reminder that a single terrified witness is a powerful but uncalibrated instrument.
Part 03
What's left on paper
Documented evidence
- Detailed, consistent testimony from Donald Shrum over decades, taken to the Air Force
- Zigzagging low-altitude luminous object; two humanoids in silvery uniform and a red-orange-eyed 'robot'
- Physical effect: whitish 'vapor' from the robot that knocked Shrum unconscious (pattern 8a)
- Defense with arrows and burning clothing; spark when the arrow hit the 'robot' (a metal indication, per the witness)
- Partial corroboration from Vincent Alvarez, also lost that night, who saw the same luminous object
- Project Blue Book investigation, with a dismissive disposition considered unsatisfactory by civilian investigators
Patterns it exhibits (1)
Entity form (1)
Location
Cisco Grove, Tahoe National Forest, California · 39.30°, -120.55°
Distribution of explanations
This case is classified among the model's hypotheses: the bar splits 100% by how much each explanation weighs (the uncertainty is spread across the hypotheses the case supports). Summed across the corpus they produce the comparable partition. It is a different question from the Probability above: that one estimates how likely the case is a genuinely unexplained phenomenon; this one splits which the explanation would be.
Modal hypothesis: Misidentification 72% · sums to 100%
Confused with: No single object identified
Structured analytical judgment, not a calibrated frequency. Forced classification: the mass the evidence cannot assign is spread across the hypotheses the case does support.
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Associated actors (1)