A gunman fired on a Dallas immigration field office from a nearby roof on Wednesday, killing one detainee and critically wounding two others, before killing himself.

Here's what we know about the suspect.

He has been identified as 29-year-old Joshua Jahn by a law enforcement official who spoke to The Associated Press on condition of anonymity.

FBI agents were seen at a house in suburban Dallas that public records link to the suspect.

He briefly worked at a Texas-based solar company and in the marijuana industry, including a stint in Washington in 2017, according to the owner of a legal cannabis farm in that state.

In 2016 the suspect pleaded guilty to felony charges of marijuana delivery, according to court records in Collin County, Texas.

He served five years probation.

The FBI said it's investing the shooting as an act of targeted violence and that bullet rounds found near the suspected shooter contained messages that were anti-ice in nature.

Investigators are seeking to determine the motive.