A judge just put a Barcelona terror suspect back on the streets - here's why

Four of the 12 suspects in last week's ISIS terror attacks in Spain are still alive, and one of them will soon be back on the streets.

National Court Judge Fernando Andreu ruled that the evidence was "not solid enough" to continue detaining suspect Mohamed Aalla, according to court documents obtained by the Associated Press.

Andreu made his ruling after the four suspects were questioned Tuesday about the vehicular terrorist attacks that killed 15 people and wounded more than 100 more, which the Islamic State has claimed responsibility for.

Two of the other suspects, Mohamed Houli Chemlal and Driss Oukabir, will be held without bail on preliminary charges of causing homicides and injuries of terrorist nature, and of belonging to a terrorism organization. Sahl El Karib, who is the owner of a cybercafe in Ripoll (the hometown of most members of the terror cell), is to remain in custody for at least the next 72 hours, as police inquiries continue.

The court documents also revealed that the terror cell was planning attacks that were much larger than the one that took place. Chemlal told the court that the cell planned to use explosives against major Spanish monuments, including Sagrada Familia, a famous church. He said the plan had been in the works for at least two months, according to The Telegraph.

Members of the extremist cell reportedly bought knives and an ax during the time between the two attacks as a fall back plan after a home that was used as a bomb-making factory exploded the day before. Once they lost access to the bombs, the terrorists rented vans and used the weapons to carry out smaller scale attacks.