SANTA FE, Texas – Dimitrios Pagourtzis, the student charged in the school shooting at Santa Fe High School, posted images on Facebook of a "Born to Kill" shirt and black trench coat before he used his father's shotgun and pistol in the attack that left 10 dead and 13 wounded, authorities said Friday.

WATCH: Santa Fe HS shooter Dimitrios Pagourtzis appears before Galveston County judge

A motive wasn't immediately clear for the nation's deadliest attack since February.

Pagourtzis, 17, was held without bond in the Galveston County Jail on charges of capital murder and assault of a peace officer, said the county sheriff, Henry Trochesset.

WATCH: Interview with Dimitrios Pagourtzis' attorneys Nicholas Poehl and Robert Barfield

Court documents show Pagourtzis hid a shotgun and .38-caliber revolver under a trench coat, walked into the school around 7:30 a.m. and began firing.

READ: These are the victims of the Santa Fe school shooting

Pagourtzis told authorities that he shot multiple people inside the school with the intent to kill them, according to the complaint. He also said he did not shoot students he liked so he could have his story told, court documents state.

Eight students and two teachers were killed.

Chris Stone, 17, and Sabika Sheikh, a foreign exchange student from Pakistan, were among those killed.

Ten other people were injured, including Santa Fe Independent School District police Officer John Barnes.

A spokesman for UTMB Hospital in Galveston said doctors treated Barnes, a 16-year-old boy and a middle-aged woman.

A spokesman for Clear Lake Regional Medical Center said doctors there were also treating some of the injured.

Guns and 'Born to Kill' shirt

Texas Gov. Greg Abbott said both weapons were owned legally by the suspect's father. It was not clear whether the father knew his son had taken them.

Abbott said that Pagourtzis' journal revealed that he wanted to kill himself after the shooting, but he admitted to authorities after he was arrested that he did not have the courage to do it.

"The red-flag warnings were either nonexistent or very imperceptible," Abbott said, though he acknowledged Pagourtzis had recently posted a picture of a T-shirt reading "Born to Kill" on his Facebook page.

Investigators with the Galveston County Sheriff's office said Pagourtzis was not on their radar prior to the shooting.

A video of Pagourtzis in court is below:

That same Facebook profile described Pagourtzis as planning to enter the U.S. Marine Corps next year, but the Marine Corps told The Associated Press it has reviewed its records and found no one by that name as either a recruit or a person in their delayed entry pool.

Abbott said at a news conference that "unlike Parkland, unlike Sutherland Springs, there were not those types of warning signs." He was referring to the Feb. 14 school shooting in Florida and one in November inside a church in a town near San Antonio.

Abbott said the early investigation showed no prior criminal history for Pagourtzis -- no arrests and no confrontations with law enforcement.

Classmates described Pagourtzis as quiet, an avid video game player who routinely wore a black trench coat and black boots to class. He had played football on the school's junior varsity squad and danced as part of a church group. Those who know him expressed shock he might be involved in the killings.

In addition to Pagourtzis, two others were detained, said Harris County Sheriff Ed Gonzalez. It is not clear if they are connected to the shooting.

PHOTOS: Scene of Santa Fe High School shooting

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Timeline of attack

According to court records, multiple law enforcement agencies responded to the school about 7:30 a.m. after receiving reports of an active shooter.

Reports said multiple people had been shot.

Between 7:45 a.m. and 8 a.m., law enforcement officers arrived at the school.

The school went on lockdown at 8 a.m.

At 8:02 a.m., court records said a "white male exited Art Lab 2 classroom of the Santa Fe High School and surrendered. The male was identified as Pagourtzis."

Explosives found on and off campus

An unknown number of possible explosive devices were found at the school and at a separate site nearby.

Bomb squads descended on the Santa Fe area after the shooting.

Officials said two bombs were found inside Santa Fe High School. Officials said CO2 cannisters with black powder and fuses were found, but neither of the devices exploded.

Authorities said explosive devices were also found at off-campus locations.

Abbott said one of the devices was powered by carbon dioxide, while another one appeared to be a Molotov cocktail.

Authorities surrounded a home about three miles away from the school, where a deputy said there was a bomb inside the house.

Investigators also swarmed a second home in a neighborhood about five miles away from the school. Officials there could be seen gearing up with battering rams, sledgehammers and saws.

It was not immediately clear exactly how either of those scenes was connected to the shooting.

Officials urged the community to immediately report anything suspicious, and not to handle any items that appear out of place.

Moments after the shooting

Store surveillance captured the moments after the shooting. Video from a nearby gas station shows students frantically making phone calls, crying and running to parents there to pick them up.

Students, parents recall shooting

One student said that he heard as many as eight gunshots. Another student reported hearing several gunshots before hearing alarms and being told to evacuate.

"I was sitting in my classroom and I heard really loud booms, but I really didn't know what they were at first," student Dakota Schrader said. "Then, I realized what they were when I heard screaming."

"I never thought it would happen here," said Tyler Turner.

"It hurts my heart to see this happening," another student said. "I don't feel safe in this town anymore ... There was nothing we could do but run."

Parents of students were told to go to the Alamo Gym at 13306 Highway 6 to be reunited with their children.

Santa Fe ISD said vehicles in the parking lot at the high school can be picked up after 9 a.m. Saturday. No one will be allowed on the property before then.

Vigils held, flags at half-staff

A prayer vigil for the victims of the shooting is being held Friday night at the Texas First Bank at 12402 Highway 6 in Santa Fe.

The Houston Astros said a moment of silence was held before Friday night’s game at Minute Maid Park to honor the victims.

President Donald Trump and Gov. Abbott ordered flags to be flown at half-staff in honor of the victims.

Santa Fe ISD to remain closed through Tuesday

The district released a statement saying all schools would be closed early next week.

"The Santa Fe Independent School District is committed to ensuring that all of our students and staff receive the care and support they need during this tragic time."All schools in Santa Fe ISD will be closed on Monday, May 21st, and Tuesday, May 22, 2018. We will update you as soon as a plan for returning to school is finalized."We know that our students and staff are going to need counseling to help them grieve. They also are going to need an outlet to share their fears and concerns. We will have additional school counselors and other support resources available to our SFISD students and staff. We will send additional information soon. Parents, please do not hesitate to ask for help if you notice a change in your child’s typical demeanor."In the meantime, please continue to pray for our SFISD community as we grieve."

Students will be able to retrieve their vehicles still at the school from 12-4p.m. Saturday.

Panicked moments earlier this year

In February, parents rushed to the high school after reports of a shooting.

Investigators later said those reports were unfounded, and that popping sounds that came from outside the school caused the panic.

More video

Below is more video from KPRC2's coverage of the shooting.