(CNN) The mother of Botham Shem Jean says her son has become the target of a smear campaign since an off-duty Dallas police officer killed him in his own apartment more than a week ago.

Officer Amber Guyger fired two shots at Jean after she mistakenly entered his apartment at the complex where she also lived, police said.

The September 6 killing has angered people nationwide and sparked protests and calls for more transparency in the investigation.

As hundreds gathered Thursday to pay tribute to the beloved man from St. Lucia, a search warrant for his apartment was made public. The document states that officers found several items in the apartment, including two fired cartridge casings, a metal marijuana grinder and 10.4 grams of marijuana.

The search warrant indicates that officers went inside the apartment looking for drugs the night of Jean's death, his mother, Allison Jean, said during a news conference Friday with her attorneys. She accused authorities of defaming her son.

"The Dallas Police Department investigators were interested specifically in finding information that could help assassinate his character," attorney Lee Merritt told reporters.

"Twenty-six years on this earth he lived his life without a blemish. It took being murdered by a Dallas police officer for Botham Jean to suddenly become a criminal."

The document does not indicate to whom the items belonged. It's unknown if a search warrant was also executed at the officer's apartment.

CNN has called Guyger's attorney, but has not heard back, and has reached out to the Dallas County district attorney's office and the Texas Rangers for comment.

"I'm calling on the Dallas officials ... please come clean. Give me justice for my son because he does not deserve what he got," Allison Jean said.

Inside Botham Jean's apartment

A CNN team visited Jean's apartment Friday, where a small memorial of flowers and a photo with his mother adorn the front door.

Several books were scattered around the unit, including C.S. Lewis' "The Screwtape Letters," which was on Jean's bedside table. Some dishes were left in the kitchen sink, and a bowl filled with ID badges, keys and notes covered the counter.

There were a few signs of the shooting: blood on the floor and a bullet hole in a wall identified by an evidence marking more than 6 feet high.

Protests and tributes for a loving son

Protesters interrupted a Dallas City Council session this week, demanding answers in Jean's death.

From St. Lucia to a small Christian college in Arkansas and to the offices of PricewaterhouseCoopers in Texas, the 26-year-old man was remembered as a loving son and brother, a hard worker and a powerful singer who enjoyed helping others.

In 2016, he graduated with a degree in accounting and management information systems from Harding University, where his family said he convinced the Arkansas school to send students to St. Lucia over the summer to do charity work.

"He was the light. He didn't look at color. He loved everybody," said minister Michael Griffin of Singing Hills Church of Christ.

"He was a person who would give you the shirt off his back, and his sole purpose in life was to make humanity better, just to make you a better person, a better human."

Officer facing charges

Guyger was charged with manslaughter in the killing and has since been released on a $300,000 bond.

The fatal shooting happened at the South Side Flats in Dallas, where Guyger and Jean both lived. Her apartment is directly beneath Jean's. Jean was home alone when Guyger, still in uniform after her shift, entered his apartment, Dallas police Chief Ulysha Renee Hall said.

The apartment's door was slightly ajar as Guyger tried to use her key, which had an electronic chip, to enter, an arrest affidavit said. When she was able to open the door, she saw the interior was almost completely dark. Guyger described seeing a large silhouette and drew her firearm, thinking a burglar was in her apartment. She said Jean ignored her verbal commands, and she fired two shots, hitting him once in the torso, the affidavit said.

The Texas Rangers is handling the investigation into Jean's death to "eliminate the appearance of any potential bias," police said.

Dallas County District Attorney Faith Johnson has said the manslaughter charge against Guyger could be upgraded when her office presents the case to a grand jury.