HOUSTON -

Houston police are looking for the men who shot and killed a security guard in north Houston over the weekend. 

It happened around 1:30 a.m. Sunday at an apartment complex near Casa Grande and Buckle.

According to police, S.E.A.L. security guard Rafael Almanza was checking on a fire that started in an abandoned apartment.  S.E.A.L. security officials said Almanza saw two or three men he thought looked suspicious and approached them.

"He stopped to detain them," HPD Sgt. Mark Holbrook said.  "At some point, he got his handcuffs out, the next thing you know he was shot in the head."

Almanza was taken to Ben Taub Hospital in critical condition and later died.

Police believe the murder and the fire are somehow linked.

"It's a total shock and an extremely difficult day," said James Alexander, Director of Operations for S.E.A.L. Security. "He [was] an excellent officer and took his job very seriously. He was just doing his job."

Police said the suspects in the shooting got away.

Alexander said Almanza, 23, leaves behind a wife and 3-year-old daughter.

S.E.A.L. Security said the company has never had to deal with the loss of one of their officers.