FORT LAUDERDALE, Fla. -

A man who wore a wire in order to help the police investigate a professor's killing testified Thursday against his father, who is accused of the crime.

Shawn Tundidor, Randy Tundidor Sr.'s younger son, testified about what happened after the April 2010 killing of Joseph Morrissey, a Nova Southeastern University professor.

Prosecutors claim Randy Tundidor Sr. killed Morrissey because he planned to evict the Tundidor family from their home, which they rented from him. Randy Tundidor Sr. is accused of stabbing Morrissey to death and setting his house on fire while Morrissey's wife was tied up and his son was asleep.

Morrissey's wife, Linda Morrissey, testified earlier this week about the ordeal. Randy Tundidor Sr.'s other son, Randy Tundidor Jr., took the stand Wednesday, saying that he had driven the Morrisseys to an ATM to get money and that he had seen his father kill Joseph Morrissey.

Shawn Tundidor testified Thursday that the morning after Joseph Morrissey's death, his father and his brother were acting strangely and asked him to turn on the news.

"I heard, 'murder in Plantation,'" Shawn Tundidor said.

Shawn Tundidor knew the victim was his father's landlord and that he was trying to evict them, so he asked his father what happened.

"He said that statement, nobody (expletive) with him and gets away with it," Shawn Tundidor said.

Then, Shawn Tundidor went to the family business, where he said he uncovered some disturbing details.

"He had knives, and all of them were there except a big one," Shawn Tundidor said.

He also asked his father about a missing pair of sneakers.

"I asked him. I said, 'Where are my white shoes?' He smiles and made a comment that, 'They weren't white when I was done with them,'" Shawn Tundidor said.

In the courtroom, one could hear a pin drop as the jury listened to Shawn Tundidor say that after Joseph Morrisey's killing, his father asked him to stop by the Morrisseys' home to run a cold-blooded errand.

"Would I go to the mailbox and get the check or something, some type of payment for rent, because since he was dead, he didn't have to pay it," Shawn Tundidor said.

Originally, police said Shawn Tundidor lied to them about what he knew, but later, he offered to wear a wire to prove his father, not his brother, stabbed Joseph Morrissey.

"He said my brother didn't know that somebody was supposed to die. My brother was only going to get money for crack," Shawn Tundidor said.

Shawn Tundidor said he betrayed his father because when his brother was arrested and charged with first-degree murder, Randy Tundidor Sr. did not seem concerned.

"He said he couldn't do nothing. He brushed it off like it wasn't nothing. Whatever, as long as it wasn't him going," Shawn Tundidor said.

During the investigation, Shawn Tundidor allowed police to search the home, and police said they found a box with gun parts and more possible gun parts in the attic.

Randy Tundidor Jr. and Randy Tundidor Sr. were both charged with first-degree murder, attempted murder, armed kidnapping and armed robbery. In exchange for his testimony, Randy Tundidor Jr. was allowed to plead guilty to second-degree murder and will avoid the death penalty.

If convicted, Randy Tundidor Sr. could face the death penalty.