FLINT, MI -- Michigan Attorney General Bill Schuette says his Flint water crisis investigation is shifting to the "the trial phase," but before it gets there, he's ramped up the stakes by charging five state and local officials with manslaughter for their actions related to the Flint water crisis.

"Our team ... will continue to pursue and gather new evidence, and we will follow aggressively any tips, information and leads that may be presented," Schuette said during a news conference Wednesday, June 14. "But as we shift to the trial phase of this investigation, we will turn to the prosecution of the individuals that have been charged with crimes."

The attorney general announced new involuntary manslaughter charges -- 15-year felonies -- against Michigan Department of Health and Human Services Director Nick Lyon, former Flint emergency manager Darnell Earley, former Flint Department of Public Works director Howard Croft, former Michigan Department of Environmental Quality Office of Drinking Water chief Liane Shekter-Smith and DEQ District Supervisor Stephen Busch.

Also charged Wednesday were Dr. Eden Wells, chief medical executive of DHHS, who faces allegations of obstruction of justice and lying to a police officer.

All of the new charges relate to a Legionnaires' outbreak and the death of a single man -- 85-year-old Robert Skidmore, one of at least a dozen fatalities tied to the outbreak.

The involuntary manslaughter charges are related to allegations by special prosecutors that Busch, Croft, Earley, Lyon and Shekter-Smith caused Skidmore's death by failing to alert the public about a rash of Legionnaires' cases in the Flint area when they had notice that additional cases would occur.

"Robert Skidmore was a family man and he and his wife had three sons, four grandchildren and three great-grandchildren," Schuette said of the General Motors retiree.

"Involuntary manslaughter is a very serious crime and a very serious charge. It holds significant weight and gravity for all involved ... I don't take that lightly ... but this investigation is about the families of Flint," the attorney general said.

Legionnaires' is a potentially fatal type of pneumonia or lung infection, according to the Centers for Disease Control and Prevention. About one in every 10 cases of the disease proves to be fatal.

Researchers and experts in the field have speculated that the Legionella bacteria may have thrived in Flint's water system after the city's water source changed to the Flint River in April 2014 because of low levels of chlorine and high levels of iron.

In addition to the manslaughter charge, Lyon was charged Wednesday with a single count of misconduct in office, but unlike lower-level state employees charged with Flint water crimes previously, neither he nor Wells will be suspended from their jobs.

Gov. Rick Snyder issued a statement Wednesday, saying Lyon and Wells "like every other person who has been charged with a crime by Bill Schuette, are presumed innocent unless and until proven guilty beyond a reasonable doubt.

"Some state employees were charged over a year ago and have been suspended from work since that time. They still have not had their day in court," Snyder's statement says. "That is not justice for Flint nor for those who have been charged."

Lyon is the highest-ranking state employee to face criminal charges for his role in the water crisis and represents the first time a Snyder cabinet member has been charged.

Schuette said he's not targeting Snyder or any other individual in state government -- only pursuing evidence or crimes.

"I've met with people, angry and frustrated, demanding that I charge, and I've heard from some who believe I've been too harsh on the Snyder administration. So be it," Schuette said.

"We only file criminal charges when evidence of probable cause to commit a crime has been established. We are not filing charges (against the governor) at this time," he said.

Investigators have attempted to interview Snyder as a part of their Flint water investigation but the attorney general said they were "not successful," declining to comment further.

Schuette also declined to grade the governor for his response to the water crisis, which occurred after emergency managers he appointed to run Flint made a series of decisions that lead to changing the city's water source from Lake Huron to the Flint River in April 2014.

Two former emergency managers, current and former employees of the state Department of Environmental Quality and DHHS, and city employees are among 15 individuals charged in the attorney general's investigation to date.

The governor has said he acted as soon he became aware of problems with lead and possible Legionella bacteria in Flint's water.

In a probable cause statement filed by prosecutors Wednesday, Lyon is accused of having received notice of the Legionnaires' outbreak at least a year before informing the public and the governor.

"As director of (DHHS), he has a duty to notify the public of any and all serious health concerns," the statement says. "After being warned about a potentially fatal health risk, defendant Lyon deliberately failed to inform the public ... (and) participated in covering up the source of Genesee County's Legionnaires' outbreak by repeatedly attempting to prevent an independent researcher from looking into the cause of the outbreak."

The probable cause statement filed in Wells' case says the chief medical executive for the state had an agreement with investigators that they would not use her own statements as evidence against her in an interview provided she made no false statements.

The statement says Wells went on to knowingly provide false information to an investigator about when she became aware of the Legionnaire's outbreak.