"He stated, 'I will kill her and I'll kill myself," Thomas said, adding that he dismissed it as "a sick fantasy."
His account came during a day-long preliminary hearing at which Patterson, 48, was held for trial on charges including first-degree murder.
Prosecutors say Patterson made good on his threat by breaking into Corado's Falls Township apartment, beating her with a metal pipe, abducting her in her car, killing her and disposing of her body. Corado, 57, has never been found despite repeated police searches in Pennsylvania and New Jersey.
"Those efforts are continuing," First Assistant District Attorney Michelle Henry said after the hearing, but prosecutors "had to establish that she is no longer with us."
That evidence came via an array of witnesses.
There was Thomas' testimony of Patterson's threats.
There was an eyewitness account of the alleged abduction given by Corado's good friend, Margaret Boyd.
Falls Township police Cpl. John Martin testified that Corado's car, found abandoned in Camden, contained puddles of blood and a blood-streaked kitchen knife identical to one found in her home.
Bucks County detective Timothy Carroll said bloodstains were on Patterson's jacket when he was arrested at a Maple Shade motel about 15 hours after Corado disappeared.
Andrew O'Rahilly, Corado's boss at a New Jersey psychiatric and detox facility, called her "the best nurse that I had" - always reliable and on time. Yet she has not shown up for work or called in since Dec. 19, he said.
Corado's son, Scott Melnick, said he spoke to her up to three times per week - but not once since Dec. 19. In her apartment he found Christmas presents for family members and a pot of soup still on the stove.
Falls Township Police Lt. Henry Ward said police have scoured areas in four counties of two states, checked all area hospitals, held multiple press conferences, and distributed Corado's photo far and wide - all to no avail.
Patterson's lawyer, Christina King, suggested in cross-examination that Corado might still be alive somewhere; that the net cast had not been sufficiently wide.
But at the end of the hearing in Fallsington, District Justice Jan Vislosky upheld all charges against Patterson, which include aggravated assault, burglary, kidnapping and several lesser charges.
Boyd described the harrowing minutes before she and Corado were abducted from the apartment. Boyd, who was later released unharmed, had been asleep on Corado's couch when Patterson broke through the locked door.
"He wasn't himself," said Boyd, who became acquainted with Patterson during the more than two years he had dated or lived with Corado. "I didn't know that person who came in that door."
Corado had apparently broken up with Patterson, who had struggled with substance abuse, after he relapsed. According to witnesses, he had been in two rehab facilities - one in Levittown, the other in Trenton- in the days preceding Corado's disappearance.
On Dec. 18, Boyd said, she and Corado had taken two large bags of Patterson's clothing to a friend in Trenton. The friend had agreed to take them to Patterson.
Boyd was sleeping on Corado's couch because the women planned to attend a concert together the next day. But around 6 a.m., Patterson burst in, yelling, "Sit down or I'll kill you," she said.
Patterson dragged Corado from her bedroom by her hair, Boyd said, beat Corado with a pipe he had brought with him, then grabbed a kitchen knife and raised it.
"I told you you weren't going to leave me," Boyd quoted him as saying. "I'll kill us both."
When Corado asked Patterson to take her to a hospital, Boyd said, Patterson ordered both women into Corado's car. But he drove past a street leading to the nearest hospital, then ordered Boyd out of the car, she said.
She called police from a nearby convenience store.
Thomas testified that he and Patterson had been sharing a room at a Levittown recovery house for a day when Patterson began talking about Corado.
"He said she was not responding to his attempts to contact her, but he seemed hopeful that she would take him back," he said.
If not, Thomas said, Patterson vowed that "no one else would have her."
Contact staff writer Larry King at 215-345-0446 or email@example.com. Follow him at www.twitter.com/kinginq.