Elected city officials and the Missouri City Police Department are grieving the death of former MCPD Det. Caleb Rule, who was killed in the line of duty May 29, according to a city press release.

Rule served as a Missouri City police officer from 2004-18 before becoming a Fort Bend County Precinct 4 deputy constable.

“We are devastated by the passing of Deputy Constable Rule,” Missouri City Police Chief Mike Berezin said in the May 29 release. “He was part of a family who took an oath to protect the community. It was an honor to serve with him in Missouri City, and our hearts are heavy for his family.”

Rule was assisting with Fort Bend County Sheriff’s Office deputies on a property check in the Sienna Plantation master-planned community when a sheriff’s deputy mistook Rule for an intruder and discharged their weapon, according to reports from Fort Bend County officials and to the press release. Rule was shot in the chest, and despite wearing a bulletproof vest, he died from his injuries, the release said.

“This is a very unfortunate incident,” Mayor Yolanda Ford said in the release. “During this difficult time, our sincere condolences go out to his family.”

An investigation into Rule’s death is ongoing.