(NewsNation) — The search is widening for convicted killer Danelo Cavalcante, and authorities now say they have the upper hand, despite Cavalcante having stolen a van and eluding the search perimeter.

Cavalcante has been on the run since breaking out of a southeastern Pennsylvania prison 12 days ago. Police said at a news conference Monday he tried to contact a former co-worker and stole a van that he drove some 20 miles.

Despite Cavalcante moving out of the previously established search zone, Supervisory Deputy U.S. Marshal Robert Clark believes police now have an advantage because he was last seen in an urban area. Previously, Cavalcante was hiding in a heavily wooded area.

“Cavalcante’s been stressed, he’s made mistakes, and now he’s kind of on our turf,” Clark said Monday on “Elizabeth Vargas Reports.”

Cavalcante escaped the Chester County Prison on Aug. 31 in Chester County, west of Philadelphia. This week, police were searching a roughly 8-square-mile zone in Chester County that included Longwood Gardens, a massive botanical garden.

Clark said the area provided Cavalcante plenty of areas to hide and said maintaining a perimeter of that size can be difficult.

“We were in about 8 square miles of heavily wooded area … and inside Longwood Gardens, there’s a massive tunnel system, the foliage in some places is extreme, almost impossible for law enforcement to pass by,” Clark said. “The perimeter was not 100% contained because it’s such a large area.”

While police have been warning residents to remain alert and lock their car doors, it appears Cavalcante found a vehicle that was unlocked with the keys inside, police said.

The 2020 White Ford Transit van that has a refrigeration unit on the top had been reported stolen by Baily’s Dairy. The company said on its Facebook page that the delivery van was stolen between 7 p.m. and 10 p.m. Saturday “while we were still here working.”

After stealing the van, police said Cavalcante drove it some 20 miles north to East Pikeland Township and Phoenixville, where he sought the help of former work associates. Cavalcante was seen on doorbell video images with a cleanshaven face and wearing a yellow or green hooded sweatshirt, black baseball cap, green prison pants and white shoes, police said.

Police believe Cavalcante is still in Pennsylvania.

“We have no other stolen vehicles, we have no other information to suggest he’s left Chester County,” Clark said.

Pennsylvania State Police said the public can expect to see a “significant” law enforcement presence around East Nantmeal Township where the van was recovered, along with other areas of northern Chester County.

Police continue to investigate the possibility Cavalcante is receiving help from someone.

“It’s not unreasonable at all to think he has help, but until we have concrete evidence of that, we’re not going to say publicly that he does,” Clark said. “We have investigators from the Marshals Service working around the clock with our state and local partners to determine exactly what happened, how he got assistance, who he got assistance from and what his next step may be.”

Cavalcante escaped from the Chester County Prison while awaiting transfer to state prison on Aug. 31 after being sentenced to life for fatally stabbing his ex-girlfriend in 2021. Prosecutors say he wanted to stop her from telling police he was wanted in a killing in his home country of Brazil.

Authorities on Friday announced the firing of the prison tower guard on duty when Cavalcante scaled a wall by “crab-walking” up from the recreation yard, climbed over razor wire, ran across a roof and jumped to the ground. His escape went undetected for more than an hour until guards took a headcount.

NewsNation correspondent Evan Lambert and The Associated Press contributed to this report.