One week on, the Clondalkin man's death is still the source of much mystery and confusion.

The Sunday Tribune has attempted to answer some of the questions surrounding his death.

How did Derek spend his last night before tragedy struck?

Last Saturday night was like any other for 24-year-old Derek. He met up with his friends and went to Bennigan's pub in Clondalkin for a few drinks and a game of pool. After Bennigan's, Derek and two of his friends got a taxi to the Arc bar near the Liffey Valley shopping centre.

In the Arc, Derek met up with his Lithuanian friend Rutha Dorolyte who worked as a lounge girl in the popular nightspot. "She dragged him up onto the dancefloor on Saturday night and he was having the time of his life, " Derek's friend Christopher Brennan recalled.

After the Arc, Derek accompanied two friends and Christopher back to Christopher's house, just around the corner from where he lived himself. There they had some food and one drink before Christopher rang a taxi for Rutha and Derek at 4am.

The pair left together in the taxi a few minutes later, even though Derek only lived a short walk from Christopher's house.

"Derek was a gentleman who always wanted to make sure everyone got home okay. If anything happened to Rutha, Derek would not be able to live with himself, " explained Chrisopher.

What happened after Derek left Rutha?

It appears that Derek ensured that Rutha got safely home before he started to make his way either on foot to Clondalkin or towards the dual carriageway in search of a taxi. The taxi which had brought him to Lucan had previously driven away.

Derek was struck by a car at a bend in the road on the main street in Lucan at around 5am. He was taken by ambulance to Blanchardstown hospital and pronounced dead at around 7.30am.

Who was driving the car?

It emerged some time after initial media reports that the car that struck Derek contained four offduty garda�. The driver in the car was with his garda girlfriend and a married couple who were also in the force. All four, who live in the Lucan area, were returning from a gathering at a private house in the area.

Is it possible that Derek was sitting at the side of the road when he was hit?

Garda� maintain Derek's injuries were consistent with the view that he was lying on the ground when he was struck by the car. While initial investigations indicate Derek was only struck by one vehicle, mystery surrounds claims that he was lying on the road.

Christopher is adamant that Derek was "nowhere near drunk enough" to do something so foolish. He says Derek had seven pints while out and another drink in his house with some food "that would have sobered him up" before leaving.

"He has often complained to us in the past about having a sore calf muscle, " he said. "It is possible that he could have been sitting down tying his laces or he may have loosened his laces to massage his calves if he was going to walk up that long hill onto the dual carriageway to hail a taxi."

Who made the 999 call?

The emergency call was made at 5.11am. Derek's mother Christine told RT� during the week that staff at the hospital told her and her husband that a taxi driver found Derek on the side of the road. The taxi driver then rang the garda� N1 and the ambulance. Superintendent Kevin Donohue, of the garda press office, said: "We are satisfied that one of the occupants of the car dialled 999. That is not to say that other people did not."

What happened after Derek was removed to hospital?

The driver was arrested in connection with the incident and taken to Harcourt Terrace garda station, where he was breathalysed and released, as he was under the legal limit. His vehicle was impounded and forensically tested, while members of the Garda Technical Bureau carried out an examination of the scene.

How did Derek's family find out the car was driven by a garda?

Christine O'Toole says that she did not know that the car was driven by a garda until she heard it on the radio on Monday morning.

She said: "In the hospital on Sunday, two inspectors came in and said they had arrested a man? but there was no mention of garda� and I heard nothing about garda� until I heard it on the radio." Garda� are now liaising closely with the O'Toole family.

How did media reports come to claim that Derek was known to garda�?

Media reports falsely claimed that Derek was "well known to garda�."

In a heart-rending interview with RT�, Christine O'Toole refuted these claims and said "any story about him having previous convictions was a total lie."

In a plea to the media she said:

"Please do not run those stories unless you know your facts. Just because he lived in Clondalkin, it does not mean that he was a drug addict or dealer. He was far from it."

Christine also pleaded with the garda� to "take back what they said about him in the papers."

Speaking in defence of An Garda S�och�na, Superintendent Kevin Donohue said: "That was not officially given to any journalist.

"There is an assumption that it came from the garda�. It is interesting that all of these theories and bits of information are from these allegedly unnamed sources. The public should be very wary of unnamed sources quoted in newspapers."

Are any more arrests expected?

A spokesman for the garda press office told the Sunday Tribune this weekend that "the investigation is ongoing."