HOUSTON, Texas (CNN) -- A gunman who took two hostages Friday at NASA's Johnson Space Center has apparently killed himself and one hostage, police said.
Another hostage has been taken to the hospital, said Houston Police Capt. Dwayne Ready.
The gunman forced the evacuation of the building and put the entire center on alert around 1:40 p.m. ET.
Earlier a witness in Building 44 on the campus reported two shots fired, said Ready, who described the suspect as a white man with blond hair, about 5 feet 9 inches and 50 to 60 years old. He had a handgun, said Ready.
Ready said he had barricaded himself in a room. The apparent suicide happened on the second floor of Building 44, he added.
The call for help came in to the Houston Police at 1:40 p.m. (2:40 p.m. ET) but it's unclear who made that call. (Watch employees being evacuated after gunfire is heard )
There is "extremely tight security" at Johnson Space Center, NASA spokesman James Hartfield said.
A NASA spokesperson told CNN that all employees have been told to go home for the day.
Space Center Intermediate School, less than a mile south of Building 44, was locked down, said Karen Permetti, spokeswoman for Clear Creek Independent School District. The lockdown was lifted at about 4 p.m. (5 p.m. ET).
The school has about 1,200 students, according to the school district.
As standard procedure, Mission Control's doors were locked, The Associated Press reported.