Trump Shooter’s Improvised Bombs Used a Radio-Control System: Report - The New York Times
A report obtained by The Times detailed the bombs’ rudimentary construction, made with the kind of initiators used for fireworks shows.
An aerial view of the complex of buildings from which a gunman fired at former President Donald J. Trump in Butler, Pa., on Saturday. Credit... Kristian Thacker for The New York Times 
Following the killing of the gunman who tried to assassinate former President Donald J. Trump on Saturday during a rally in Butler, Pa., investigators discovered two improvised explosive devices in the would-be assassin’s car that used a radio-controlled initiation system designed for commercial fireworks demonstrations.
Details on the improvised bombs were in a document released by a federal government task force on Monday to law enforcement departments across the country.
The New York Times obtained a copy of the document, called a “quick look” report, on Tuesday.
The two devices in the car owned by Thomas Matthew Crooks, 20, of Bethel Park, Pa., were almost identical in construction, according to the task force’s report. Each contained a cardboard tube filled with a gray powder that was described by a police bomb technician as having “an odor of nitromethane” and appeared to contain prills — essentially small pellets.
While the report does not contain a laboratory analysis of the gray powder, the description suggests the presence of a fertilizer, which is often packaged in prill form. According to the National Institute for Health, nitromethane is sometimes used as a fuel in racecars and has a “strong disagreeable odor.” It can be purchased online.
The combination of certain kinds of fertilizers and fuels is a common method for creating homemade explosives, such as the ammonium nitrate-based device Timothy J. McVeigh used to destroy the Alfred P. Murrah Building in Oklahoma City, Okla., in 1995, killing 168 people.
Whether or not Mr. Crooks attempted to detonate the devices is unclear, but the report described them in a manner that cast doubt on their viability as weapons.
Notably, the devices in Mr. Crooks’s car used a type of radio-control system for initiating fireworks displays, in which a single hand-held transmitter can broadcast a signal to multiple small receivers. These in turns send current to an electric match — a wire with a pyrotechnic compound on one end — that produces a small flame to ignite the firework.
The two devices in Mr. Crooks’s car were composed of ammunition cans — one metal, and one made of plastic — that each had a cardboard tube inside, filled with the gray powder recovered by police bomb technicians. Each cardboard tube had the head of an electric match inserted, and they were connected to a radio receiver unit.
The receivers shown in photos from the report appear to be identical to a model called Alpha Fire made by RFRemotech, a company based in Guangzhou, China.
The report shows that law enforcement officers recovered a set of 10 radio receivers from Mr. Crooks’s home along with electric matches. According to RFRemotech’s website, a set containing 12 Alpha Fire receivers and one transmitter can be ordered online for $192, while a set containing a second transmitter costs $216.
The product listing for the Alpha Fire says that it can reliably initiate fireworks from a distance of about 6,500 feet.
“We are sorry for the assassination attempt on your former president Donald J. Trump,” said Yukie He, an account manager for RFRemotech, in an email early Wednesday. “We checked all history sales, but not any records of a sale of our products to Thomas Matthew Crooks.”
John Ismay is a reporter covering the Pentagon for The Times. He served as an explosive ordnance disposal officer in the U.S. Navy. More about John Ismay
A version of this article appears in print on
, Section
A
, Page
15
of the New York edition
with the headline:
Bombs in Gunman’s Car at Trump Rally Had Radio Control