HOUSTON -- A security guard shot two men as they ambushed and tried to rob him Tuesday afternoon on a northwest Harris County street, officials said.

Homicide detectives told News2Houston the security guard, Eduardo Gutierrez, was transporting money when his vehicle was surrounded around 1:30 p.m. on Ella at Kuykendahl.

"They had a vehicle in front, a vehicle behind and one on the side is my understanding. When he came to a stop to go no further, some of the (men) exited the vehicles, jumped out and went around to begin to demand money, at which time, he pulled his weapon and shot," said Bruce Williams, with the Harris County Sheriff's Department.

Two gunmen were hit. Lifeflight transported one man to Memorial Hermann Hospital, while an ambulance took the other to Ben Taub Hospital. There's no word yet on their conditions.

Gutierrez was not injured.

"I was just turning the corner, just turning the corner and seen the security guard shooting everywhere -- shooting that way and shooting this way," said Terry Spellman, a witness.

Detectives said the gunmen carefully planned the armed robbery.

The managers of the security company where the guard worked said he was commissioned by the state and trained to use his weapon.

"He's a good guy. He has a lot of experience -- good man," said Carlos Toruno, with Spartan South Houston Security.

A third and possible fourth robber fled on foot and are still on the loose.

News2Houston worked on this story through their local newspaper partnership with Houston Community Newspapers and the Humble Observer.