HOUSTON — A pro-Palestinian message was written on the gun used by a woman accused of firing rounds at Joel Osteen’s Lakewood Church on Sunday, two sources briefed on the preliminary investigation told ABC News.

However, a motive behind the Sunday afternoon shooting has not been determined. Sources said investigators are feverishly going through the social media and writings belonging to the suspect, who is believed to be Genesse Ivonne Moreno, 36, according to law enforcement sources.

Detectives believe Moreno fired as many as 12 shots, according to a law enforcement official briefed on the investigation.

Two people, including a 7-year-old boy, were shot and are in the hospital.

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The shooting happened during a Spanish-language service, and could be heard on the church livestream.

Authorities said the shooter was killed by two off-duty officers.

It all unfolded as thousands of people were packed inside the megachurch.

Overnight, agents with the FBI, Texas Rangers, and ATF raided a Conroe home believed to be connected to the suspect. Video from the scene shows a large law enforcement presence.

Houston police said the woman, who had a 7-year-old boy with her, walked inside Lakewood Church at 1:53 p.m. Sunday, wearing a trench coat and armed with a long rifle. She reportedly started shooting immediately.

A Houston police officer and a TABC agent who were working off-duty inside the church quickly returned fire, killing the woman.

As the woman went down, officers reported that she threatened to have a bomb. Officers with the bomb squad searched her car and backpack and found no explosives.

The 7-year-old boy who was with the woman was shot. As of Monday morning, the child is in critical condition at an area hospital. A 57-year-old man was also shot in the leg.

Authorities said it’s unclear who fired the shots that hit the child and the man.

“We don’t understand why these things happen, but we know that God is in control. We’re going to pray for that (little boy), and pray for the lady that was deceased and her family and all, and the other gentleman,” Pastor Joel Osteen said. “Believe that we’re going to stay strong and we’re going to continue to move forward.”

Houston Police Chief Troy Finner said patrols will be increased at places of worship across the City of Houston.

Panic spread quickly as people inside the church started running and trying to get to safety. Some managed to get outside the building, but could not leave because officers locked down several blocks surrounding the church.

Meanwhile, inside the building, others did what they could to try to hide.

Some people were stuck inside the church for hours — waiting for police to give an all clear. During the chaos, some parents were separated from their children, who were inside the church day care.

ABC13 reporter Charly Edsitty happened to be in the area running errands when the shooting happened. She spoke to a father and son who were leaving Lakewood as the shots were fired.

“I saw this lady running. She almost fell down the stairs. I told her, ‘Hey, you dropped something.’ She said something in Spanish that I couldn’t understand. And then I saw someone else running down the steps. That’s when I heard two gunshots,” the father said. “I was going towards my family and I heard another gunshot coming closer. So I was like ‘I can’t go up there now.'”

The witness was separated from other family members – who were not hurt — and had to wait until loved ones were able to leave the building.

Meanwhile, Lakewood says their community is devastated over what happened. They are scheduled to hold their usual Wednesday service online, with the next in-person service set for next Sunday.