The Boyzone manager, who knew Stephen since he auditioned for the band in 1993, said he was still numb with shock over the star's tragic death.
"I just can't get my head around it and don't know how I'll get over it," he admitted. "I've just been walking around in a daze. I am still in shock. I just cannot believe this has happened.
"I'm desperately trying to keep busy, but I'm all over the place."
Louis told the Daily Mirror of the closeness between the two. "He used to text me during X Factor, telling me who he liked," he revealed.
"We had some incredible nights out in London. We'd gossip, have fun, fall around being silly… he never changed."
The music mogul also revealed there would be a private family wake for Stephen's family on Friday evening followed by a funeral in Dublin on Saturday morning.
Louis voiced his sorrow as a post mortem showed Stephen – whose body was found in his £1 million Majorca holiday home on Saturday – died of natural causes.
A build up of fluid on the lungs – known as acute pulmonary oedema – was ultimately responsible. Most cases are are related to heart failure or the early stages of heart disease.
The results were welcomed by the singer's grieving family. His mum Margaret believes her son died from a previously undetected heart condition that has plagued his family. "It has lifted a huge burden off our family's shoulders," she said.