The unidentified shooter was one of three Fort Bend County sheriff’s deputies on the scene, according to a press release from the sheriff’s office.

The victim, 37-year-old Caleb Rule, was a deputy constable with Fort Bend County’s Fourth Precinct, the Houston Chronicle reported.

Both agencies were responding to a call in Missouri City, a southwest Houston suburb, around 1:45 a.m. Friday, the release said.

A woman had reported a person running from a vacant house, according to local NBC affiliate KPRC.

Once inside the house, one sheriff’s deputy mistook Rule for an intruder and fired at him, according to the release. Rule was wearing a bulletproof vest but died later that morning at a hospital.

Fort Bend County Sheriff Tony Nehls said the deputy who fired had more than 20 years of law enforcement experience, the Chronicle reported.

“We are heartbroken over this,” Nehls said. “We are praying for everyone involved.”