Randolph Sanders was careful.

Lurking in a breezeway on the morning of Jan. 13, with a gun tucked into his duffel bag, Sanders hid his face under a cap and bulky headphones.

He was careful, police said, not to look at the security cameras that captured him when he approached his boss - Kim Jones - and shot her in the back of the head as she waited for a bus.

And when Jones, 56 and a mother of two, didn't show up for work that day - as her stunned family gathered behind the crime-scene tape at 12th and Jefferson Streets - Sanders was careful to behave as a concerned coworker should.

He called her phone and left a message, asking if she was all right. As news of her death spread, he gave an interview to TV news, expressing his shock and dismay. He showed up at Jones' funeral to pay his respects.

But detectives from the Homicide Special Task Force, trawling through hours of surveillance video, were already tracing the killer's path from the crime scene. They would eventually track the bulky man dressed in black to a 2007 Yukon - Sanders' vehicle.

And they knew from Jones' coworkers and friends that there was some sort of tension between the two.

That was enough to bring him to the homicide unit for questioning on Saturday.

After two weeks of hiding in plain sight, Sanders gave a full confession.

Police said Jones suspected him of stealing funds - about $40,000. He was convinced that she would report him to authorities and that he would lose his job at Turning Points for Children, the organization where they worked, police said.

On the morning Jones was killed, she had scheduled a meeting with the Department of Human Services, which funds Turning Points.

Sanders, 36, knew she was going to turn him in, Homicide Detective James Clark said.

"He laid in wait, and he ambushed her," Clark said.

Sanders had been hired by Jones in 2012 and served as the assistant director of the nonprofit's Families and Students Together (FAST) program, an after-school outreach designed to strengthen parents' bonds with their children.

Turning Points said in a statement Monday that it believes the alleged misappropriation of funds was "an isolated incident" but will hire a third-party investigator to look into the matter.

An investigation into the allegedly stolen funds is ongoing, but Clark said police believe Sanders had been stealing gift cards meant for families participating in the FAST program and keeping them for himself.

He has been charged with murder and related offenses.

Police found weapons during a search of Sanders' home, Clark said. But detectives continue to search for the gun Sanders said he used to kill Jones. Sanders told police he discarded it after the killing. Clark would not say where Sanders allegedly dropped the gun.

Clark and Deputy Commissioner Richard Ross on Monday praised detectives' hard work on solving the case, which Ross described as "nothing short of miraculous."

Efforts to reach Jones' family were unsuccessful Monday. A mother of two grown sons, she had married her longtime partner in a December ceremony.

The Philadelphia Daily News reported Monday morning that Jones' son, Andre Jourden, said he shook Sanders' hand at his mother's funeral.

"The fact that he could even look any of my family members in the eye and shake my hand the day of my mother's funeral is just flat-out unimaginable," Jourden wrote in an e-mail. "I now put my faith in our justice system to truly give him what he deserves for murdering a respected, generous, loved, and selfless woman that did nothing but try to help people."

A neighbor, Wesley Hatton Jr., said Jones was quiet, well-liked, and devoted to her church and her work with children.

"I'm glad they caught him. It puts everything at peace," Hatton said. "Justice should be done."