(CBS) LOS ANGELES A 26-year-old man was in custody Monday for his alleged role in the fatal shooting of a 3-year-old girl in Baldwin Hills two weeks ago, but the 17-year-old suspected gunman remains at large, Los Angeles police said.

Laron Lee Larrimore was arrested Friday afternoon at a motel in the 3500 block of Slauson Avenue, police said.

Larrimore is accused of driving the getaway car following the attack that claimed the life of Kaitlyn Avila and left her father, Cesar Avila, wounded, according to Deputy Chief Charles Beck of the Los Angeles Police Department.

The suspected gunman, Jonathan Durrell Banks, remained at large and is believed to be hiding somewhere in Los Angeles, Beck said.

A $50,000 reward was offered for information leading to the arrest of Banks, who was described by police as African American, 6 feet tall and weighing about 200 pounds.

"We are actively requesting the public's help to find this vicious criminal, this vicious murderer of a child before he escapes the net of justice," Beck said during a news conference at the LAPD's downtown dispatch center.

The attack happened about 2:45 p.m. on Sept. 24.

Cesar Avila and his two daughters had just arrived at their home in the 4500 block of Pinafore Street after lunching at a McDonald's when a gunman walked up, shouted a gang slogan and opened fire, authorities said.

Kaitlyn was killed and her father was critically wounded, according to police. Kaitlyn's 6-year-old sister, Kassey, witnessed the shooting, but was not hurt.

The suspects allegedly sped away in a gray Chevrolet Pacifica.

"We're heartbroken, we're very heartbroken for the death of my daughter," Avila said, his voice breaking.

"We ask the suspect to turn himself in," he said. "Even though it won't bring my daughter back, at least we know more innocent people won't get hurt. I don't care so much for what he did to me, but for what he did to my daughter."

Beck said that detectives from the LAPD's Southwest Division "worked 24 hours a day" for the last two weeks to solve the crime, and that several witnesses came forward with critical information.

"We found several reasons for the cooperation, one being the universal tragedy of the death of a 3-year-old, and two, the callous nature in which this was instituted," Beck said. "This was not an accident."

The motive for the attack remains under investigation. Both suspects are known gang-members and may have mistaken Avila for a rival, according to Beck.

It was unclear whether the attack was racially motivated, but police held community meetings with Latino and black residents in South Los Angeles to keep tensions from rising.

"Obviously there's a racial difference between the suspects and the victims in this case, but we believe it is the monster of gang activity in South Los Angeles that is that cause of this shooting," Beck said.

"It's very hard going home," Avila said. "Walking around my house and knowing I won't see my daughter again, it's too much."

Anyone with information about the shooting was asked to call police at (213) 485-2417 or (877) LAWFULL.