Pretoria, South Africa (CNN) -- It was the middle of the night, Oscar Pistorius says, and he thought an intruder was in the house. Not wearing his prosthetic legs, feeling vulnerable in the pitch dark and too scared to turn on the lights, the track star pulled his 9mm pistol from beneath his bed, moved toward the bathroom and fired into the door.

It was only after he called to girlfriend Reeva Steenkamp -- whom he thought had been in bed beside him after a quiet evening -- that he realized something horrible might have happened, he told Chief Magistrate Desmond Nair in a statement read by his lawyer during his bond hearing Tuesday. Prosecutors dispute the version of events that Pistorius detailed in his statement.

Pistorius says he broke down the locked bathroom door -- at one point in the statement saying he kicked the door in, at another saying he used a cricket bat to break it down -- then scooped up the mortally wounded Steenkamp and carried her downstairs after for help.

"I tried to render the assistance to Reeva that I could, but she died in my arms," he said in the statement. "I am absolutely mortified by the events and the devastating loss of my beloved Reeva."

Pistorius' affidavit in alleged murder of girlfriend

While prosecutors and defense lawyers agree Pistorius shot Steenkamp, the track star denied intentionally killing her, in the statement read Tuesday.

Prosecutors say they believe Pistorius put on his prosthetic legs, picked up his gun and walked to the bathroom where Steenkamp, 29, had locked herself -- apparently after a heated argument -- and shot at her four times.

Three of the bullets struck Steenkamp, who died soon after. Her funeral was Tuesday.

Pistorius spent much of the hearing sobbing and heaving at the mention of his girlfriend's name, at one point forcing Nair to stop the proceedings to ask him to compose himself. His family stood nearby, huddling during breaks and appearing to pray. During parts of the hearing, Pistorius' brother placed his hand on the suspect's back.

During Tuesday's hearing, Nair upgraded the charge against Pistorius to premeditated murder, saying he could not rule out the possibility that the track star planned Steenkamp's death. But Nair said he will consider downgrading the charge later.

The allegation of premeditation makes it more difficult for Pistorius' attorneys to argue he should be released on bail pending trial. To win bail, the defense must argue that "exceptional circumstances" exist that would justify Pistorius' release.

The session ended Tuesday afternoon with no decision on bail for Pistorius, 26. Prosecutors said they needed time to study the affidavits read in court before deciding how to proceed.

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In the statement read by his lawyer, Pistorius said he would not try to flee or influence any witnesses if he is allowed out on bail, and argued that his release wouldn't be a danger to public order.

The hearing is scheduled to resume Wednesday morning.

A tragic mistake?

In his statement, Pistorius said Steenkamp came over February 13, opting for a quiet dinner in over a night out with friends. They wrapped up the night with a bit of television in bed for him, some yoga for her. She had brought him a Valentine's Day present to open the next day.

After the couple had gone to bed, he said he got up in the early hours of February 14 to close the balcony door in his bedroom when he heard a sound in the bathroom.

Pistorius said he'd been a victim of violence and burglary in the past, and realized with terror that contractors who worked at the house had left ladders outside.

Fearing someone had entered the home through the open bathroom window, moving in the dark on the stumps of his amputated legs, Pistorius grabbed his pistol from under the bed and yelled at the intruder to get out.

"I fired shots at the toilet door and shouted to Reeva to phone the police. She did not respond and I moved backwards out of the bathroom, keeping my eye on the bathroom entrance," Pistorius said in his statement. "Everything was pitch-dark in the bedroom and I was still too scared to switch on a light."

"When I reached the bed, I realized that Reeva was not in bed. That is when it dawned on me that it could have been Reeva who was in the toilet. I returned to the bathroom calling her name," he said.

He said he threw open the balcony door and screamed for help, put on his prosthetic legs and tried to kick in the door to the separate room inside the bathroom containing the toilet. Then, he said, he picked up a cricket bat, smashing panels out of the door before finding a key and unlocking it.

"Reeva was slumped over but alive," he said.

Pistorius said he called for help and was told to take her to the hospital himself.

He carried her downstairs and tried to help but, but she died.

"I cannot bear to think of the suffering I have caused her and her family, knowing how much she was loved," he said.

But he said he did not mean to kill her, and protested the charges against him.

"I fail to understand how I could be charged with murder, let alone premeditated murder because I had no intention to kill my girlfriend," Pistorius said in the statement.

"We were deeply in love and couldn't be happier," he said."I loved her and I know she felt the same way."

A premeditated murder?

Prosecutors, however, painted a different picture.

They rejected Pistorius' claim that he mistook her for a burglar, saying it would make no sense for an intruder to hide behind a locked bathroom door.

Instead, they say Pistorius armed himself, attached his prosthetic legs and walked 7 meters (23 feet) to shoot Steenkamp through a bathroom door after a heated argument.

Defense attorney Barry Roux questioned the state's argument, asking how prosecutors would know Pistorius had put on his prosthetic legs and walked to the bathroom before shooting his girlfriend.

Police were alerted to the shooting by neighbors, and residents had "heard things earlier," police spokeswoman Denise Beukes said.

Authorities said there had been "previous incidents" at the home, including "allegations of a domestic nature," but did not provide details.

Detectives are investigating the blood-stained cricket bat found in the home, Johannesburg's City Press newspaper reported. They are trying to determine whether it was used to attack Steenkamp, if she used the bat in self-defense, or if Pistorius used it to try to break down the bathroom door, the newspaper said.

Final farewells for Steenkamp

As the drama in court unfolded, friends and family mourned Steenkamp at a private funeral in her hometown of Port Elizabeth.

"There's a space missing inside all the people she knew that can't be filled again," her brother Adam Steenkamp told reporters outside.

Steenkamp was a law school graduate whose modeling career was on the rise. She landed the cover of FHM magazine and recently appeared on a reality TV show.

On Sunday, South Africans heard Steenkamp's voice one last time after her death, when the national broadcaster aired a pre-recorded episode of the show. The model talked about her exit from "Tropika Island of Treasure," on which local celebrities compete for prize money.

"I'm going to miss you all so much and I love you very, very much," she said, blowing a kiss to the camera.

Case rivets fans

The case of the global sports hero known as the "Blade Runner" has riveted stunned fans around the world.

As he walked into court in a blue shirt and gray suit, frenzied photographers snapped away, prompting the judge to demand they stop.

The scene was a far cry from the packed stadiums that erupted in applause whenever the double-amputee competed against men with legs.

On social media, sentiment appeared to mixed. "Oscar Pistorius is telling us rubbish," one Twitter user posted.

But others were more supportive after hearing Pistorius' story. "I for some reason believe Pistorius after reading his affidavit!!," another person tweeted.

Robyn Curnow reported from South Africa; Holly Yan reported and wrote from Atlanta. CNN's Nkepile Mabuse also contributed to this report.