What was in Flint's water that caused 12 people to die?

The drinking water in Flint, Michigan was contaminated with lead and other harmful chemicals due to the city's switch to a new water source without proper safeguards in place. The lead in the water was particularly dangerous for children and pregnant women, and has been linked to developmental delays and other health problems. The contaminated water is believed to have contributed to the deaths of at least 12 people.