Federal and local law enforcement last week began investigating the cause of an explosion at a duplex in northern Virginia last Monday after a more than 3-hour stand-off between a resident and Arlington police, CNN reported.
In a December 5 statement, the Arlington County Police said that officers were at the duplex to serve a search warrant on 56-year-old James Yoo over suspicions that he had been firing over 30 rounds from a flare gun into the surrounding area earlier in the day.
The officers arrived at the duplex at around 5:00 p.m. on December 4 and attempted to communicate with Yoo both by phone and through loudspeakers. However, the suspect remained barricaded inside the building.
When an emergency response team breached the front door, Yoo fired several rounds from inside. The other residents of the duplex were evacuated and the fire department shut off the gas to the property.
The officers were continuing their attempts to engage with the suspect to get him to surrender when at about 8:25 p.m. the building exploded.
Human remains later discovered at the scene were presumed to be Yoo’s. The medical examiner was expected to positively identify the body and determine both the cause and manner of death.
The explosion prompted the evacuation of several nearby homes with ten households impacted by the blast.
Since last Monday’s incident, investigators discovered “concerning social media posts” made by Yoo.
Investigators found rambling and often incoherent conspiracy theories posted on Yoo’s LinkedIn account in which Yoo railed against law enforcement, media outlets, and government officials. In a post from December 1, Yoo also accused his neighbors of spying on him and collecting intelligence about him for their handlers.
Yoo had also repeatedly contacted the FBI in recent years through online tips, phone calls, and letters, according to DC Field Office Assistant Director in Charge David Sundberg.
The FBI and the ATF are assisting the Arlington County Fire Department and local law enforcement in investigating both the explosion and the suspect, Arlington County Police Chief Andy Penn said.