The family of Dalian Atkinson, who died after police repeatedly Tasered him, have told of their “agony and frustration” at still not knowing why officers used force against him.

Atkinson, a former Premier League football star, died aged 48 in August after a clash with police during which he was shot with a Taser three times outside his father’s home in Telford, Shropshire.

His funeral is on Saturday and his family told of their pain as they waited for the results of inquiries into his death.  His sister Elaine said: “We want to celebrate Dalian’s life but the way that he died while he was so vulnerable casts such a dark shadow over everything. Every day is filled with agony and frustration because we still do not know what happened nor understand why such force was used on him.”

The IPCC inquiry is expected to last until late spring or the summer of 2017.

Shortly before his death, Atkinson had been diagnosed a with serious illness affecting his kidneys and his blood pressure, and then with pneumonia.

Elaine Atkinson said: “We all did our best as a family supporting Dalian and being there for him. One comfort we have is that he knew that he was loved and he told us this. Dalian was supposed to have been admitted to hospital for treatment on the day he died.”

Hours before his death, Atkinson, a former player for Aston villa and Real Sociedad, spoke to another of his sisters, Otis, about “his worries and fears about his deteriorating health”. He told her: “All I ever wanted was to make people happy. I played football the way that I did because I wanted to entertain. I wanted everyone to go home with smiles on their faces.”

West Mercia police said the incident that led to his death came when officers were called at 1.39am to reports of concerns for a person’s safety. Atkinson is believed to have argued with and assaulted his father when he went to his home. 

After police arrived, there was a clash with officers. Atkinson collapsed and medical staff tried to revive him for 35 minutes, but he failed to respond and was pronounced dead 90 minutes after police arrived.

The key issues in the criminal investigation will be whether the decision to use force was justified and, if so, whether the level of force was proportionate to Atkinson’s behaviour.  The two officers have been issued with gross misconduct notices and interviewed under criminal caution. The IPCC has stressed its decision to launch a criminal investigation did not mean the officers did anything wrong.

In their statement, Atkinson’s family said he realised his dream to be a top-flight footballer and was a “kind, caring and protective brother, with a lively personality; he was funny and cheeky”.

They said his ill health had affected him badly: “He understandably struggled to come to terms with the sudden diagnosis of serious illness affecting his kidneys and his blood pressure during the last six months of his life. 

“He tried to stay positive, but it was heartbreaking for us to see a further deterioration in his health with pneumonia, leaving his light and energy significantly reduced.”

Shortly after Atkinson’s death, his brother, Kenroy, 53, said the ex-footballer was “in a manic state and depressed” at the time of the incident and had attacked their 85-year-old father, Ernest, at his home before police were called.