SANTA FE, Texas -- Ten people were killed in a shooting Friday morning at a high school south of Houston, Texas Gov. Greg Abbott said. School district Police Chief Walter Braun said that explosive devices were found in Santa Fe High Schooland the surrounding area.

According to law enforcement sources, nine students and a teacher were killed in the shooting, CBS News senior investigative producer Pat Milton reports. At an afternoon press conference, Abbott said that another 10 people were wounded.

The suspect in custody was identified as Dimitrios Pagourtzis, 17, Galveston County Sheriff Henry Trochesset said in a statement. He was being held without bond on a charge of capital murder. Harris County Sheriff Ed Gonzalez said the suspect was believed to be a student at the school.

Abbott said that two people in interest were being interviewed by authorities. He didn't identify them.

According to a law enforcement source, the suspect posted to social media "Dangerous Days" with a pentagram on Friday before the shooting, Milton reports.   

Abbott said the suspect had said that he wanted to commit suicide after the shooting.

"He gave himself up and admitted at the time that he didn't have the courage to commit the suicide," Abbott said.

Police found pressure cookers and pipe bombs around the school, a law enforcement source told CBS News.

There was an active search for explosives, a federal law enforcement source told CBS News justice and homeland security correspondent Jeff Pegues. Authorities were in the process of rendering them safe and asked the public to call 911 if they see anything suspicious.

Sources confirmed to Pegues that authorities were searching property related to the suspect.   

"We experienced an unthinkable tragedy at our high school this morning," Superintendent Leigh Wall said in a message posted to Facebook. 

Two students and a school resource officer were shot and injured in the shooting, CBS News has learned. Another law enforcement officer was also injured but was not shot.

One hospital reported treating eight wounded patients. Six were treated and released. One was listed in critical condition, and another in fair condition.

The suspect had a shotgun and a .38-caliber revolver, Abbott said. The suspect's father owned the weapons legally, Abbott said, adding that he didn't know whether the father was aware his son had obtained the weapons.

Student Damon Rabon told CBSN that he looked out his classroom door with a substitute teacher after hearing several loud bangs and saw the gunman.

"Black trench coat, short kind of guy, had a sawed-off shotgun," Damon said.

The substitute teacher then pulled the fire alarm in the hopes of alerting students and faculty in other areas of the school and getting them to evacuate.

Tyler Turner, a senior at the school, told KHOU-TV that his friend saw "some kid" with a gun. When teachers and students were outside after the fire alarm was pulled, shots were fired, Turner said.

"As soon as the alarms went off, everybody just started running outside," 10th-grader Dakota Shrader told reporters, "and next thing you know everybody looks, and you hear boom, boom, boom, and I just ran as fast as I could to the nearest floor so I could hide, and I called my mom."

Turner said he ran behind some trees, heard more shots, jumped a fence and ran to a car wash. He said he saw firefighters treat a girl who had a bandage around her knee and may have been shot.

One student told Houston television station KTRK in a telephone interview that a gunman came into her first-period art class and started shooting. The student said she saw one girl with blood on her leg as the class evacuated the room.

"We thought it was a fire drill at first but really, the teacher said, 'Start running,'" the student told the television station.

The student said she didn't get a good look at the shooter because she was running away. She said students escaped through a door at the back of the classroom.

Authorities have not yet confirmed that report.

Students from the high school were being transported to another location to reunite with their parents.  

A parent told CBS affiliate KHOU-TV that some students were evacuated to an auto shop near the campus.

Aerial footage from the scene showed students standing in a grassy field and three life-flight helicopters landing at the school in Santa Fe, a city of about 13,000 residents roughly 30 miles southeast of Houston.

In Washington, President Trump initially reacted to the shooting on Twitter.

"School shooting in Texas. Early reports not looking good. God bless all!" Mr. Trump said.

Later, while speaking at an event on prison reform, the president said it was a "very sad day."

"This has been going on too long in our country," Mr. Trump said. "Too many years, too many decades now. We grieve for the terrible loss of life and send our support and love to everyone affected by this absolutely horrific attack. To the students, families, teachers and personnel at Santa Fe High, we're with you in this tragic hour, and we will be with you forever."

According to a law enforcement official, the FBI was offering assistance, Milton reports.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives also said it was responding.

There was a large law enforcement response to the same school in February when it was placed on lockdown after students and teachers said they heard "popping sounds." Santa Fe police swept the campus but found no threat.

Read more about this story on CBSNews.com.