PEABODY — Mohammadreza Zangiband and Marven Abda on Monday left to make deliveries from the roast beef restaurant in Lynn where they’d worked together for more than a year.

They had no idea it was the last time they would see each other alive.

A short time later, Abda learned Zangiband, an aspiring commercial pilot and Iranian immigrant, had been shot dead about 5:50 p.m. as he took a shortcut en route to delivering food in Lynn. The man known as Sina was Abda’s best friend, neighbor, colleague, and fellow immigrant.

“What’s going on in this world? I just don’t get it,’’ Abda, 24, asked Tuesday as Zangiband’s relatives mourned privately inside their Salem home. “Out of all those people, Sina? That Sina? I mean, nobody can believe it.’’

No one has been charged with killing the 24-year-old Zangiband, but authorities Tuesday identified Brian G. Brito, 21, as a person of interest in the shooting.

State Police arrested Brito on Route 1 South in Peabody about 10:40 p.m. Monday after troopers spotted him driving the same gray Audi bearing a New Hampshire license plate that was sought in connection with the Lynn homicide, officials said.

After the arrest, troopers learned North Andover police were searching for a man for an alleged armed robbery and sexual assault that happened after the killing in Lynn. North Andover authorities said their suspect looked like Brito and was driving an Audi.

According to authorities, a man wearing a ski mask and brandishing a firearm went into a Richdale convenience store on Chickering Road in North Andover and ordered the clerk to lock the doors.

The assailant, who was later identified as Brito, sexually assaulted the clerk, emptied the cash register, and stole lottery tickets before fleeing, police said.

Brito informed the victim that he had killed somebody, according to court records.

Troopers were told the North Andover suspect wore a black ski mask and black gloves, and they recovered both items from Brito’s vehicle, a police report said. They also found a loaded, 9mm semiautomatic with one round in the chamber in Brito’s jacket. A loaded magazine and a box of 9mm ammunition were found in the pockets of his cargo pants, the report said.

Brito, who has addresses in North Andover and Manchester, N.H., was arraigned Tuesday morning in Peabody District Court on charges of illegal possession of a firearm and ammunition and motor vehicle violations. Not guilty pleas were entered on Brito’s behalf.

He remained out of view during the arraignment at the request of his defense lawyer, Rebecca Whitehill. She declined to discuss Brito or the allegations he faces.

Judge Richard Mori ordered Brito held without bail pending a dangerousness hearing April 10. North Andover police have obtained an arrest warrant accusing Brito of aggravated rape, kidnapping, and armed robbery in the convenience store attack, authorities said.

He is expected to be arraigned early next week on those allegations, the Essex district attorney’s office said.

Investigators haven’t disclosed why Zangiband was targeted.

“We have no concrete information as to the motive,’’ said Carrie Kimball Monahan, a spokeswoman for the Essex district attorney’s office. “We believe the person responsible is in custody and is being questioned.’’

Zangiband’s colleagues at Atha’s Famous Roast Beef became worried about him Monday after receiving calls from customers who said they hadn’t received their deliveries, Abda said. Zangiband wasn’t answering his cellphone, he said.

Abda said he spotted a Lynn police cruiser at a Cumberland Farms near the restaurant and spoke with the officer about Zangiband.

The officer told him “something bad’’ had happened to Zangiband, but wouldn’t elaborate, Abda said. A short time later, investigators went to Atha’s and told employees that Zangiband had been killed, he said. The restaurant closed. Abda said he doesn’t know Brito.

“My heart was broken,’’ said Ali Alshammari, 26, a driver for a neighboring restaurant who saw Zangiband on Monday. “When I heard that, I thought it was a car accident. I couldn’t believe it.’’

A relative, who asked not be named, said Zangiband was an innocent man who enjoyed life.

“He just loved flying in the sky and loved driving in a fancy car,’’ said the man, who identified himself as Zangiband’s brother-in-law.

Abda, an Iraqi immigrant, said he met Zangiband when they were students at Lynn Classical High School. After graduation, he said Zangiband moved to Florida and began studying to become a pilot.

He moved back to Massachusetts a little more than a year ago and worked at Atha’s while he continued to work toward becoming a commercial airline pilot, Abda said.

Zangiband often told Abda that he was like family to him: “I love you. I have no brother. I love you like a brother,’’ Zangiband told him.

Zangiband loved to eat Iranian kebabs, but also enjoyed American fare such as buffalo chicken, his friend said. He amassed an impressive shoe collection, storing as many as 50 to 60 pairs in his closet, Abda said.

Next week, Zangiband was to turn 25. He planned to celebrate by renting a Porsche or Lamborghini, Abda said.

“I just can’t believe this happened to him,’’ he said. “I told you. We’re just like brothers.’’

John R. Ellement of the Globe staff contributed to this report. Laura Crimaldi can be reached at laura.crimaldi@globe.com.