07/01/2012 09:32 am ET Updated Jul 04, 2012

Celena Hollis, Denver Police Officer Who Died After City Park Jazz Concert Shooting, Funeral Draws Thousands (VIDEO)

Thousands lined the streets and packed into a Denver church to honor Denver Police Officer Celena Hollis, who was shot to death in City Park during a jazz concert while trying to break up a fight.

Officers from the Denver Police Department and Detroit Police Department, where 32-year-old Hollis began her career, sat alongside U.S. Sen. Michael Bennet, Gov. John Hickenlooper and Denver Mayor Michael Hancock in the Denver First Church of the Nazarene in Englewood Saturday. Outside, people lined Hampdon Ave. and Quebec streets to watch the lengthy motorcade of police cars, firetrucks, ambulances and search and rescue units.

Hollis had been off-duty but in uniform when she was shot in the head June 24. Twenty-one-year-old Rollin Oliver, whose possible ties to locals gangs is still being investigated, was arrested on suspicion of firing the shot that killed Hollis.

Denver Police Chief Robert White has told the media that Oliver gave conflicting statements about the extent of his gang affiliations when he was booked, and stressed that the investigation is still ongoing.

"I am not going to give out information unless I am sure it is right," White said.

Before the City Park shooting, the ACLU of Colorado had planned to host a "Summer without Police Violence" rally on Saturday, but rescheduled it in deference to Hollis' memorial.

A former police classmate of Hollis' shared his sentiments on the Denver Police Department's Facebook page:

I think if Officer Hollis could see what we saw today, she would be proud. She would be proud of her strong family members, of her brothers and sisters in blue (from all over the country) and she would have been proud of the citizens of Denver.

It was made very clear today that we can bridge the gap between the Department and the citizens. We can bring this community back together and make a difference.

So as a classmate of Officer Hollis... I want to extend my thanks to the Officers, Firefighters, Paramedics, and her family that made this day all the more special. But I truly want to thank the citizens of our community that continue to show their support of us. I want you to know that you are appreciated and that we will continue to strive to protect your streets and your families. We will continue to place ourselves in harms way without the desire of fame, fortune, or recognition... to ensure that our city is safe.

We lost a great Officer today. They say, "Heroes Live Forever"... so I know she wont be forgotten.

According to The Denver Post, songs played during Hollis' funeral included "Purple Rain" by Prince and Michael Jackson's "P.Y.T. (Pretty Young Thing)."

Hollis was a single mother, and is survived by her 12-year-old daughter, Amyere, who spoke at her funeral.

The Wayne County Sheriff's Department in Detroit, Mich. told The Associated Press that they were planning to host their own tribute to Hollis on Saturday by stopping their vehicles and turning on their lights and sirens for 15 seconds.

On Friday Hancock announced that City Park Jazz and city officials will be hosting a musical tribute to Hollis at City Park on Sunday from 6-8 p.m.

People are being encouraged to show their support by wearing purple, Officer Hollis' favorite color, joining the silent vigil and donating to a college fund created for Hollis' daughter.

“The death of Officer Hollis was a tragic loss for the City of Denver. But we must emerge out of the shadow of mourning and come together to strengthen our city’s resolve,” Hancock said in a media statement. “We stand here today to ask our community to join us – right here – for City Park Jazz this Sunday. We will honor this wonderful woman, and stand united to send a strong message to our community that we will not condone such crimes.”