A vigil is held March 20 for slain Prince George's County police officer Jacai Colson, who was killed by friendly fire during a shootout that followed an ambush at the police station in Palmer Park, Md. (Nikki Kahn/The Washington Post)

At a McDonald’s drive-through in College Park, the man taking Jacai Colson’s order didn’t ask if he wanted fries with that.

He asked if Colson wanted to buy marijuana.

Although Colson was off-duty, the undercover narcotics officer “instantly went into work mode,” said Aaron McMullen, a fellow Prince George’s County police officer who also was off-duty that evening and went out socially with Colson.

“He started rapping, and he got his number,” McMullen said.

Soon after, Colson developed a case, excitedly calling his supervisor to report: “Dude! I got him.”

Colson was always ready to work, no matter when and how the opportunity presented itself. It is that dedication to policing that friends and colleagues have been recalling as they mourn the 29th Prince George’s police officer to die in the line of duty in the department’s history.

Family, friends and fellow officers will honor Colson at a series of memorial services set to start Thursday.

Colson, 28, was killed by friendly fire in a March 13 gun battle launched by a man who police say plotted and carried out an ambush on officers outside a police station while two of his younger brothers recorded the shooting on cellphones.

Colson drew fire toward himself, allowing other officers to take position and take down the shooter who ambushed them, Police Chief Henry Stawinski III has said.

“That day, without reservation, he was there,” said Lt. Robbie Loveday, Colson’s former supervisor. “He pulled up in the middle of something and didn’t back down.”

The three brothers have been charged in connection with the gun battle.

Almost a week after his death, Colson’s squadmates and friends gathered at the Prince George’s police union, where an image of Colson soon will join the portraits honoring other fallen officers.

They remembered the competitive athlete who was usually an hour early for football practice, the good-natured companion who always made time to have a beer with buddies before finishing up paperwork and the dedicated detective who was always thinking 10 steps ahead of the criminals.

A native of the Philadelphia area, Colson attended Randolph-Macon College in Ashland, Va., where he played football and earned a degree in business and economics.

Hassan Shonekan, 28, was friends with Colson for 11 years and attended college with him. The two played football together, and Colson was often the first to show up at training sessions.

During one football drill, the coach had Colson play as a defense back with Shonekan on the other end.

“As soon as the quarterback said, ‘Go!’ Jac smacked me 10 times in the head,” Shonekan said.

“What are you doing?” Shonekan remembered asking his friend.

“I have to do whatever I can to keep you off the line,” a grinning Colson told him.

Colson was the friend in the group who kept the party and the jokes going. He’d be the one to sweet talk the flight attendants during a trip home from New Orleans into getting approval for a photo in the cockpit with pilots or the one to transform a simple Super Bowl watch party into a memorable night.

Although he was a loyal Philadelphia Eagles fan, Colson was happy for an excuse to have some fun when the Baltimore Ravens won the Super Bowl a few years ago.

“‘Let’s just go to Baltimore,’” McMullen recalled Colson saying after the game ended. “I said, ‘Now? It’s midnight.’ ”

But, swayed by Colson’s enthusiasm for life, everyone hopped into the car and found themselves an hour away from home, reveling with Baltimoreans in the postgame excitement.

“I realized that night, I never laughed that hard ever,” McMullen said. “I hurt from laughing.”

Colson joined the Prince George’s police department four years ago. His grandfather was a police officer, and Colson wanted to follow his lead. Colson — who dreamed of working for the FBI or the Drug Enforcement Administration — quickly became an undercover narcotics officer after a stint in patrol.

Loveday said the young detective was eager to do the work, regardless of the hour and peril.

“In narcotics, you can get call-outs to go to scenes, and they can be in the middle of the night,” Loveday said. “He was one of the guys I could always count on. He was there ready to go.”

Colson was a good undercover cop, his colleagues say. He grew a long beard — a la James Harden of the Houston Rockets — to work undercover, and he often had a ball cap flipped backward and cocked to the side of his head.

He’d glide through a room and ask, “What’s the science, baby?” a greeting he relied on hoping to draw a laugh from whomever he asked. With an ability to make conversation with anyone and to think on the fly, he’d net some solid cases.

As a detective, Colson was strategic, sizing up each situation — from small drug buys to big busts — as if in a giant game of chess.

“Jai would break it down,” said his undercover narcotics partner, who spoke on the condition of anonymity because of the nature of his work. “He would ask: ‘What are we going to do if we get robbed tonight? What if a dude punches me in the face? Which way are we going to run? Which way are we going to take cover?’ He was always 10 steps ahead of the game.”

He also knew not to let minor snags keep him down.

Once, he and his partner went to a gas station, hoping to buy marijuana from a drug dealer and catch him in the act of selling. After chatting with the man for some time, they followed him to a house, where the man came out with a bag. This was it, the officers thought: the transaction that would seal their case. But when the man opened the bag, there were no drugs.

“It was a bag of CDs,” Colson’s partner said.

Colson returned to the office, laughing, with an album to show his sergeant.

Although Colson was a younger officer, his death has hit the department hard.

Colson was shot by another officer, but his supervisor and some colleagues said they don’t blame the officer who fired the fatal shot.

“It’s just one of those things where any blame we put on anybody goes toward the three brothers that got locked up,” said the supervisor, who spoke on the condition of anonymity to protect his identity for undercover work. “The whole situation doesn’t happen if they didn’t do what they did. It was an intentional act by them that caused Jacai’s death.”

After Colson graduated from the academy, he told one classmate with certainty that they would wind up working together. A year later, the department promotions list came out: They’d both be working undercover narcotics.

“‘I don’t know how you guessed it,” the undercover officer, who spoke on the condition of anonymity, told Colson.

“‘You got to have faith, and you got to believe me,’” Colson said, playfully wagging his finger. “‘We’re going to retire together.’”

Colson’s colleague chokes up at the memory, teary-eyed.

“Wait for me at the Pearly Gates,” Colson’s squadmate said. “We’ll meet there together.”