Carpenter said students are able to opt-out of those alerts, but the system is designed to send notifications to every student.
A message was posted on Facebook about 1 p.m. The first posting the college made on its main Twitter account was about 2 p.m. A notice did not appear to have been posted on the North Harris campus' Twitter page at all.
There were more than 10,000 students on the campus at the time of the shooting, said Jed Young, a school spokesman. Lone Star College's North Harris campus sits on 200 acres and opened in 1973. It is illegal to carry a concealed gun on a college campus in Texas.
"The policy of the board is that it's a gun-free campus," Carpenter said. "That doesn't mean that we can observe every ... we've got 19,000 students on this campus. We don't search students that come on the campus."
According to college officials, administrators have been actively talking about how they should deal with a shooter on campus. On Tuesday morning, the college president sent faculty members a link to a video that demonstrates what to do in an active shooter situation.