"Richard was always bringing me flowers. Christopher would kiss me," she says. "I'm still longing for my children."

Alia's voice breaks. Tears stream down her cheeks. Then she sobs. It's the cry of a mother who has lost a child. Only, she has lost four.

Her weathered hands tremble as she clutches a plastic bag with a small notebook and a handful of photos of her sons -- the only pictures she has left.

She explains how they grew up dirt poor, like pretty much everyone in the slums of Davao. Drugs and crime plagued their neighborhood.

When former prosecutor -- now President -- Rodrigo Duterte was first elected mayor of his hometown in 1988, Davao was dubbed "the murder capital of the Philippines."

Crime was out of control. Residents were justifiably scared to walk the streets at night. The new mayor declared open season on criminals by encouraging police and vigilantes to use lethal force to rid them from the streets.

By the time Alia's sons came of age, Duterte's brutal war on crime was in full effect in Davao. Alia tried to steer her boys away from the gangsters that seemed to rule the backstreets and alleys of the slums. But the lure of easy money, combined with peer pressure, proved irresistible.

"My son Richard, the eldest, was about 15. And he was in the gang. But I told him please get out of that because Duterte already warned on the TV that your sons and daughters who are really into something (crime) should get out of the city because they will be killed."

Richard was first to die, in 2001 according to Alia. She says Christopher was killed later that year, and in 2002, Bobby was stabbed to death—all of those cases remain unsolved.

Fernando was in hiding for nearly five years before being stabbed to death in 2007 -- all of those cases remain unsolved.

Police told Alia her sons were thugs, "serial thieves," unable to be rehabilitated.

Alia says death has become common in the city.

"That's the problem with our government here in Davao. People will do nothing even if they see somebody is being shot. They just don't care," Alia says.

During our interview, passing teenagers heckle Alia for openly criticizing Duterte, whose nationwide approval ratings are around 80%.

"People should speak up, especially the victims," Alia says. "If they remain silent, the suffering will continue."

She's one of the few in Davao who seems willing to say the killings must stop.

Duterte is the first Philippine president from the island of Mindanao where Davao is located, a point of immense local pride.

"He treats everyone as if they are part of a big family. If you did something wrong, then definitely you will be disciplined. If you did something bad you will be punished," says one woman at the night market.

"He's done a lot for the city in terms of keeping peace and order and inspiring people to be better citizens. He's a hands-on leader," another man says.

Duterte has denied any involvement.

"This is wrong. We have to put a stop to this. Because if this continues it will destroy us as a country, as a nation," Picardal says.

"It is bringing out the worst in a lot of people ... Most of (those killed) will be poor, most of them will be users, and the problems of poverty will still be there. It is not addressed. It is going to bring us to ruin."