HOUSTON -- A disgruntled patent attorney fatally shot another attorney before turning the gun on himself inside a northwest Houston office building Thursday morning, police told KPRC-TV in Houston.

Officials said a contracted patent attorney apparently shot a full-time attorney shortly after arriving at work. The contracted attorney then turned the gun on himself.

The shooting happened at the legal department on the fifth floor of the Cameron building, inside the contract attorney's office at about 8:40 a.m.

"There were some individuals around when this shooting occurred. We have separated those individuals who were closest to the scene so that our homicide investigators can speak with them. Anybody else on the floor has also been detained so that we can ask them if they are aware of anything that may have motivated the shooting," Houston Police Department Sgt. Dwayne Ready said.

Authorities said the shooting might be the result of the contract attorney learning that he was being laid off. Both men were in their 50s or 60s and sources told Local 2 that the full-time attorney was the contract attorney's boss.

Police found a .357-caliber revolver and a semiautomatic weapon underneath the chair in which the shooter was sitting.

About 700 employees were evacuated from the building as officials investigated but were allowed back inside at about 9:30 a.m. The fifth floor remained closed.

Authorities have not released the victims' identities.

In a statement, Cooper Cameron President, Chairman and CEO Sheldon R. Erikson said, "We are deeply saddened by the tragic events of this morning that resulted in the deaths of two people at Cameron office building. Our thoughts and prayers are with their families, friends and co-workers at this difficult time."

The company said it would provide counselors to employees.

The Cameron building houses a division of Cooper Cameron oil services company, which makes pressure control systems for oil drilling.

The building had no metal detectors, but the police sergeant said it had security-card control access and that all workers' cars were registered with the company. The building also had security cameras, and Ready said homicide detectives were reviewing the tapes.