Hundreds of MTA drivers joined Pena's family at the Church Center for the United Nations to pay their respects to the driver killed when an allegedly drunken driver behind the wheel of a stolen truck slammed into his bus on West 14th Street last week.
"I just offered the family my condolences," de Blasio said after leaving the memorial. "I let them know we're thinking of them, we're praying for them."
Pena lay in an open casket wearing a charcoal grey suit. A flower arrangement in the shape of his bus driver's badge stood behind him.
"It's great everyone is giving their support," Pena's younger sister, Araseli Pena, said outside the viewing. "He deserved this. Everybody loved him."
The family of the 17-year bus driver have also set up a website in his honor, WilliamPena.org, with a link to a crowdfunding site to benefit Pena's beloved 17-year-old daughter, who is starting college in the fall.
"Daddy, if you're listening I want you to hear me, this is for you," Gabriela Pena wrote on the site. "I miss you but [you're] gone, [you're] not coming back, writing this is the hardest thing and never thought I would have to do," wrote Gabriela on the website. "We were inseparable always together and always being clowns with each other."
The site also provides details about the memorial and funeral service for the popular city driver, as well as information about the court appearances of Domonic Whilby, who prosecutors said drove the stolen truck with a .18 blood alcohol content.
The fundraising page has received more than $4,500 in donations from 103 supporters.
The family is hoping to raise half a million dollars by June 13 to help support Gabriela's college education and pay off the mortgage on Pena's New Jersey home where Gabriela lives with her mom.
The funeral service will be held at The Church of Saint Paul the Apostle on Columbus Avenue and West 60th Street Thursday at 11 a.m.
Whilby was partying with his uncle, model Tyson Beckford, into the early morning hours of Feb. 12 when he allegedly stole a delivery truck from a parking garage at the Dream Downtown hotel on West 16th Street at 5:20 a.m., prosecutors said.
Whilby sideswiped two other vehicles and ran at least two red lights before slamming into Pena's bus at 14th Street and Seventh Avenue, according to prosecutors.
Whilby has been held without bail on charges including vehicular homicide, assault and manslaughter.
Pena's brothers, Eriberto Pena and Alex Pena, showed up at Whilby's last court appearance each wearing one of William's work shirts, the New York Post reported Tuesday.
The brothers, along with other family members and friends, plan to attend each of Whilby's hearings.
“We want justice for our brother and we will be here,” Eriberto told the Post.