Ukrainian postgraduate student Pavlo Lapshyn, 25, pleaded guilty at the Old Bailey to the murder of 82-year-old grandfather Mohammed Saleem in Birmingham in April and plotting to cause explosions near mosques in the West Midlands.
The father of Pavlo Lapshyn, who murdered a Muslim pensioner and planted three bombs at mosques, told ITV News his son had previously detonated a "chemical experiment" at home in Ukraine.
Sergey Lapshyn said: "Well, once, when he was home alone, he did some chemical experiments. It was very hot, and the mix detonated. Of course we got back home immediately and none of our neighbours said anything bad.
"They just asked us not to be so loud. We talked to Pavel it about it and it looked like he stopped experimenting."
Lapshyn's father also added that he had concerns over the case: "I've got a lot of questions. First, I don't believe he killed anyone. I just can't believe this. Second, fascism...he never was involved in politics.
"Okay, he may have been stressed, something clicked and he got certain ideas. But then, why did he try to blow up a mosque, not a synagogue? There's no logic. I've got many questions, and not many answers."
A Ukrainian student has admitted stabbing an 82-year-old Muslim pensioner within five days of arriving in the UK.
Police have released images showing Ukrainian student Pavlo Lapshyn preparing for and carrying out attacks in the Midlands.
A timeline leading up to the conviction of Pavlo Lapshyn, who murdered pensioner Mohammed Saleem and set bombs off outside mosques.