Story highlights Oscar Pistorius once tweeted a photo of himself at a gun range

Nike pulls an ad featuring Pistorius and the word "bullet"

Reeva Steenkamp tweeted Wednesday about her "boo" making her a shake

Pistorius was arrested for assault in 2009 but the case was dropped , police say

A beloved model is dead, those who knew her are in mourning, and one of the world's most admired Olympians is charged with her murder after a Valentine's Day shooting in South Africa.

Oscar Pistorius , a Paralympic runner who blazed new terrain by competing in last summer's Olympics, is accused of killing his girlfriend, Reeva Steenkamp . A shooting took place inside his upscale home in Pretoria, South Africa, early Thursday, and only the two of them were there at the time, police said.

Shock waves from the incident quickly reverberated across the world, casting a shadow over the man known as the "Blade Runner" for his achievements on prosthetic limbs.

Pistorius will be named officially as the suspect when he appears in court Friday, in keeping with South African law. Authorities have already announced that the suspect is Pistorius' age.

Investigators gave no motive for the alleged killing.

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"Previous incidents" at the home, police say

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

A police spokeswoman said there had been "previous incidents" at the home, including "allegations of a domestic nature." They did not detail what those may be.

Pistorius was arrested and accused of common assault in 2009, but the case was thrown out because of a lack of evidence, police told CNN on Thursday.

That incident involved Pistorius allegedly slamming a door during a party, and a piece of the door fell off and hit someone, said Capt. Marissa Van der Merwe of South African police.

Police are not aware of any prior incidents between Pistorius and Steenkamp, Van der Merwe said.

Some South African media outlets suggested Pistorius may have mistaken Steenkamp for an intruder. South Africa has a high crime rate, and many homeowners keep weapons to ward off intruders.

Beukes said those reports did not come from police. There did not appear to be signs of forced entry at the home, she added.

"This is a very quiet area, and this is a secure estate," Beukes said.

A pistol was recovered at the scene, police said.

In November 2011, Pistorius tweeted a photo of himself at a gun range, and wrote that he had "a 96% headshot over 300m from 50 shots! Bam!"

Pistorius cooperating with police

Pistorius has made no public statement. His spokeswoman Kate Silvers said the athlete is "assisting the police with their investigation but there will be no further comment until matters become clearer later today." Police also said Pistorius is cooperating.

He arrived Thursday at a police station in Pretoria.

Beukes said the state will oppose bail. That means the 26-year-old, who was among the men featured in People magazine's "Sexiest Man Alive" issue, could be behind bars, at least temporarily.

Pistorius is not being brought to court Thursday because the public prosecutor needs more time to prepare the case, police spokeswoman Katlego Mogale told CNN.

A model's life violently cut short

Steenkamp, 29, had been looking forward to Valentine's Day, encouraging her Twitter followers to "get excited" for the holiday.

On Wednesday, she tweeted , "It's a beautiful day! Make things happen. Starting my day off with a yummy healthy shake from my boo," followed by a smiley face. "Boo" is a term for boyfriend.

"She was the kindest, sweetest human being; an angel on earth and will be sorely missed," Capacity Relations, the agency that represented her, wrote on Twitter.

She was "just a great, fun presence of a person," said Hagen Engler, former editor of the magazine FHM. He described her as "a bikini model, beautiful, gorgeous girl" with a "wicked" sense of humor. She understood the industry and was intelligent and fun to work with, he said.

Pistorius' father, Henke, told the South African Broadcasting Corp. his son was "sad at the moment."

"I don't know nothing. It will be extremely obnoxious and rude to speculate," the father said. "I don't know the facts."

Nike pulls ad

Nike pulled an ad featuring Pistorius from its website Thursday. The ad showed Pistorius taking off for a run, and contained the words" I am the bullet in the chamber."

The company issued a statement expressing "sympathy and condolences to the families concerned following this tragic incident." The company added that it will not comment further, noting that the situation is a police matter.

Other Pistorius sponsors -- including prosthetics manufacturer Ossur, British Telecom, and Oakley, which makes sunglasses and other products -- expressed condolences and said they had no further comment at this time. Fashion company Thierry Mugler had no comment.

As Olympian, Pistorius faced controversy

Pistorius, a double amputee, competed against able-bodied runners during the London Olympics, triggering controversy as some said the prosthetic limbs gave him an advantage. His legs were amputated below the knee when he was a toddler because of a bone defect. He runs on special carbon fiber blades.

Pistorius was initially refused permission to enter the Olympics, but he hired a legal team to prove that his artificial limbs did not give him an unfair advantage -- and was allowed to compete.

While he did not win a medal, his presence on the track was lauded by many people around the world as an example of victory over adversity and dedication to a goal.

He smashed a Paralympic record to win the men's 400m T44 in the final athletics event of the 2012 Games.

In an October interview with CNN's "Piers Morgan Tonight," Pistorius discussed the "massive blessing" of inspiring people around the world.

"Being an international sportsman, there's a lot of responsibility that comes with that, so having to toggle that and remembering, you know, that there are kids out there, especially, that look up to you -- it's definitely something that you need to keep at the back of your mind."