Police have released this composite drawing of the man who sexually assaulted a six-year-old girl in Surrey on Friday. ((Courtesy RCMP))

A Lower mainland businessman is offering a $20,000 reward for information leading to the arrest of the man accused of sexually assaulting a six-year-old girl.

Police say the attack happened on Friday evening in the area of 139th Street & 62nd Avenue when the girl was walking home with her brother, 12, and his friend,15. Police say a man with a knife threatened the boys, separated them from the girl and assaulted her.

Developer and hotel owner Bob Cheema said he called the child's father on Monday morning offering his help.

"I do a lot of business in Surrey, and I have a young family," Cheema said. "I understand that part — you know, if you have a young family, that it's not the money kind of thing ... This can happen to me or anybody if this person is at large in the community in Surrey."

Cheema said he hopes the money will trigger someone to come forward with information on the attack.

Police released a composite sketch of the attacker on Monday afternoon. They are looking for a dark-skinned young man — possibly Hispanic, Asian or South Asian — in his late 20s or early 30s with very short, dark hair.

Police also said they've spoken at length with the victim, her brother and his friend and are confident the children are telling the truth about the incident.

In another development, the girl's father told reporters he waited 24 hours before reporting the incident to police because his wife withheld details of the attack.

"It's not like we were trying not to tell the police or whatever and take care of it ourselves because I honestly didn't know," the man said, with his wife and daughter standing at his side.

"So, I said don't phone the police. From what I thought at the beginning, it wasn't worth phoning them 'cause I am not a very much of a policeman-liking type of person. But the next day — later on that night, I guess, almost the next day early in the morning — my wife told me the truth, and I told her to immediately phone the police." 

The parents cannot be identified under terms of the Youth Criminal Justice Act since that would identify the victim. 

Police said that before they were called, the girl's father tried to find her attacker by papering the neighbourhood with warning letters.