On Valentine's Day morning, Nikolas Cruz's 5-foot-7-inch, 120-pound frame couldn't be shaken from his bed in suburban Parkland, Florida.

Cruz, 19, lived on a lush street dotted with tropical plants with a family who had opened their home to him after the death of his adoptive parents. The father, James Snead, normally delivered Cruz to his adult GED class on the way to work. Wednesday was different.

"I don't go to school on Valentine's Day," the freckle-faced Cruz insisted.

At his former high school five miles away, a new day was beginning.

Marjory Stoneman Douglas High School's free breakfast was winding down. The 7:40 a.m. bell signaling the start of first period loomed.

The "daily morning affirmation" that day on the public school's website came from the late self-help author Louise Hay: "Life supports me in every way possible."

"I love you," she told Alyssa.

That day, teachers collected applications for the National English Honor Society. Members of the tennis teams raised money with the sale of hoodies, yoga pants and other items. Classmates exchanged Valentine's Day carnations sold for $1 in a cafeteria. At lunchtime, some students left $60 deposits for graduation rings.

Parents wait for news after reports of the shooting at Marjory Stoneman Douglas High School.

The school day went on as normal. But before the last bell of the day could ring, Marjory Stoneman Douglas High School -- whose motto tells students to "be positive, be passionate" -- would be the scene of one of the deadliest mass shootings in modern US history

'So many shots'

It was no secret to those that knew him that Cruz was fascinated with guns and violence.

He posed with guns and knives on Instagram, showed guns to a former classmate and kept a semiautomatic rifle in a lockbox in his room. A former classmate said Cruz would sometimes introduce himself as a "school shooter."

The orphaned youth also battled mental illness and depression, his attorneys said later , exacerbated by the recent death of his adoptive mother. She had repeatedly called police to the home to help deal with his violent outbursts. A defense attorney called him "a broken child."

Cruz eventually made it out of bed that Valentine's Day. He exchanged a number of unremarkable text messages with the son of the family he stayed with and called an Uber.

At 2:19 p.m., a gold-colored Uber vehicle dropped him off at the school he once attended. A school employee recognized him.

Cruz had been expelled for unspecified disciplinary reasons. Now he was back, with a .223-caliber AR-15 rifle concealed in a soft black case.

The employee alerted a colleague that the former student was "walking purposefully" toward a school building.

The school, like many across the US, had made active shooter training drills its protocol.

Cruz entered the school building at the east stairwell. He pulled the rifle out of its bag.

At some point, Cruz activated a fire alarm.

Nicole Baltzer, 18, was in trigonometry class. In 10 minutes, the school day would be over. Why was the fire alarm blaring again?

There had been a fire drill earlier in the day. This second one sowed confusion, and students began to scurry from classrooms.

Cruz began the massacre, initially targeting people on the first floor. Bursts of semiautomatic fire echoed in the corridors.

"So many shots," Baltzer said. "They were very close."

Freshman Kelsey Friend and her classmates in geography class rushed back into their classroom once they heard the shots.

Her teacher, Scott Beigel, 35, unlocked the door for them. There he stood, like a sentry, ushering his students to safety.

She thought Beigel would follow her inside. He didn't. The sound of gunfire grew louder.

Friend wanted to believe this was just another drill. A more realistic one maybe, with police officers shooting blanks. Other students thought firecrackers were causing the staccato bursts.

Then Friend realized this was no drill. Beigel's body crumpled to the floor at the classroom door.

Later she would say, "I am alive today because of him."

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"Nikolas Cruz, Nikolas Cruz, who came in on campus with a backpack."

Another transmission provided more information: "I'm being advised by ROTC students that he was kicked out last year. We're still looking for a photo -- he worked at a Dollar Store on Magnolia. Last name spelling is C-R-U-Z."

'I'm in a school shooting right now'

Terrified, the students turned to the familiar: cell phone cameras, text messages, Snapchat and Twitter. They gave the world a glimpse into their horror as it unfolded. Trembling hands. Blood-curdling screams. Bullet-strewn classrooms. Blood-stained floors. Bodies.

Family members embrace outside the school.

"I'm in a school shooting right now."

He hunkered down under a desk in a dark classroom. The shooter stalked the corridors outside.

I am in a school shooting right now... — Aidan Minoff (@TheCaptainAidan) February 14, 2018

Minutes later, Aidan tweeted again.

"My school is being shot up and I am locked inside. I'm f***ing scared right now."

The tweet included photos of students huddled on the floor. They checked their phones between desks. One appeared to be texting.

In 17-year-old Hannah Carbocci's Holocaust history class , a bullet pierced the wall. She thought of her big sister, her protector.

Pop-pop! Pop-pop! Screams. More gunshots.

Hannah, under a teacher's desk, texted her 19-year-old sister Kaitlin.

Hannah:

kaitlin there is a shooter on campus

i am not joking

call 911 please

send them to douglas

Kaitlin:

hannah what

are you serious rn

Hannah:

kaitlin i am not joking they just shot through the walls someone in my class is injured

i am not joking

call mom and dad

'The Kevlar would slow the bullet down'

Assistant coach and security guard Aaron Feis, a graduate of the School, put himself between three students and the shooter, an act of bravery that surprised no one.

Feis was shot. He died after he was rushed into surgery.

Colton Haab, a 17-year-old junior and football player, would say later, "That's Coach Feis. He wants to make sure everybody is safe before himself."

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As the shots rang out, Haab ushered 60 to 70 people to shelter in the Junior Reserve Officers' Training Corps room. They shielded themselves behind sheets of Kevlar used for Junior ROTC marksmanship practice.

"The Kevlar would slow the bullet down," Haab thought.

Teacher Melissa Falkowski hid in a large closet with nearly 20 students. She brought them in from the hallway. Some were crying. Other were calling or texting family with words of gratitude and love.

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Cruz wasn't done. He roamed the first-floor halls before going to the second floor. He shot a victim in another room.

On the third floor, he dropped his rifle and bag. He then ran out of the building, blending in with students and staff who were pouring out of the school, many with their hands in the air.

Responding officers suspected as much.

"Someone checking the IDs of those kids before they get up and leave the area?" an officer radioed to dispatch.

Later came another transmission: "Attention all units, be advised -- a repeat of the last instruction -- juveniles being loaded onto the buses are going to park. The IDs need to be checked of the juveniles before they get on the buses. Make sure that Nikolas Cruz isn't part of this group."

'I knew at that point she was gone'

But Cruz slipped away. He bought a drink at a Subway sandwich shop inside a nearby Walmart. Later, he sat at a McDonald's for a few minutes.

Police helicopters buzzed overhead. Tearful students reunited outside the school with their parents.

Lori Alhadeff, hours after dropping off her daughter Alyssa, raced back to the school when she learned of the shooting.

"I knew at that point she was gone," she said. "I felt it in my heart." Alyssa didn't make it.

Other students remained on lockdown. Not taking chances, some called 911 before letting SWAT teams members enter.

"Student in Classroom 1255 says somebody's pushing on her door -- is that a police officer? Any units pushing on 1255?" a police dispatcher asked.

Students file out of the school. Many were afraid the shooter was still a threat.

"Yes, yes, 1255, that's going to be us," an officer responded.

"You want them to open it or do you want me to tell them to stand down?"

"Tell her to open her door, have her open her door right now!"

As student Masiel Baluja evacuated, she put her book bag on her back just in case she got shot from behind. She ran toward students and teachers. She jumped a fence before police escorted her to a group of students assembled near Walmart. She could see her mother, but Masiel was suspicious of those around her.

"I didn't know if any of them were shooters or not," Masiel said later, fighting back tears. "I felt very uncomfortable because anybody can be a shooter."

'He looked like a typical high school student'

A police officer made contact with Snead, the father who had taken in Cruz after the teen's mother died last fall.

Snead said he had spoken with Cruz, who told him he was at the McDonald's near campus.

Nearly 80 minutes after the first 911 call, a police officer from nearby Coconut Creek spotted a young man walking along the side of a residential street. The description and clothing matched the shooter's.

Suspect Nikolas Cruz was arrested in a nearby neighborhood.

"He looked like a typical high school student," officer Michael Leonard said. "For a quick moment I thought, 'Could this be the person? Is this who I need to stop?'"

Leonard pulled over and Cruz, wearing a maroon polo shirt with the school's eagle mascot on the sleeve, surrendered without incident.

"We have the suspect detained," came the radio call at 3:41 p.m.

The suspect in the deadliest school shooting since Sandy Hook was caught and 17 people were dead.