Washington (CNN) -- Internal Revenue Service chief Steven Miller may have been among the first people to be blamed for a scandal now consuming the agency and buffeting the Obama administration, but at least one powerful House Republican is confident he won't be the last.
"This isn't just going to end up being just one person's responsibility," House Ways and Means Committee Chairman Dave Camp told CNN on Thursday in an exclusive interview. "This is a group of people. Decisions are going to be made with lots of sign off."
"We're going to need to find out to what extent others knew, and why really this whole policy was implemented," the Michigan congressman said.
Camp will lead a committee hearing on Friday examining recent IRS targeting of conservative groups applying for federal tax-exempt status.
Miller, the hearing's star witness, submitted his resignation on Wednesday after being told to do so by Treasury Secretary Jack Lew.
He will leave the post in June.
In another development, the commissioner of the IRS Tax Exempt/Government Entities Division, announced his plans to retire. Joseph Grant also will leave in June, according to an internal IRS memo provided to CNN.
"It seems as if there's a culture of discrimination at the IRS and I want to get to the bottom of it," Camp said. It appears that people with "a certain type of political view were targeted, while others were more progressive or liberal views were left alone."
The congressman added he's "very suspicious" the targeting operation was politically motivated.
"We don't have the information to back (that suspicion) up," he said. "That's why we're going to need to conduct this hearing and others until we get to the bottom of it. And we're not going to stop until we know all the facts."
Camp said that President Barack Obama -- who has called the agency's misconduct "inexcusable -- needs to take responsibility for IRS behavior.
"Ultimately, the president is responsible for the administration," Camp said. "And the IRS is part of the administration."
CNN asked Camp why Miller didn't inform Congress earlier about the improper targeting of conservatives. Miller first became aware of the issue in May 2012, according to the agency.
"I don't know why," Camp said. "If it is incompetence, it's incompetence that goes into a level of wrongdoing. I mean, there really can be errors of omission and errors of commission and to me, to not have any awareness of this ... seems grossly negligent."
As head of the IRS, you "have people's most personal and private financial information," he added. "You have this authority to strike great fear in them through audits and interviews and questions."
According to a report by the agency's inspector general released on Tuesday, the IRS developed and utilized a faulty policy to determine whether applicants were engaged in political activities, which would disqualify the groups from receiving tax-exempt status.
The policy went into effect in early 2010, the report said, and "used inappropriate criteria that identified for review Tea Party and other organizations applying for tax-exempt status based upon their names or policy positions instead of indications of potential political campaign intervention."
The report stated that IRS officials did not consult anyone beyond the agency about the development of the screening criteria.
Camp called the report "disappointing."
"We're seeing reported in the press that other individuals that weren't applying for tax- exempt status were brought into the IRS and questioned about views that were unrelated to their tax return," he said. "So I think this may be larger."
Asked whether Friday's hearing in the Republican-controlled committee will be viewed as merely another battle in Washington's ever-escalating partisan war, Camp noted that the hearing "was called in a bipartisan way."
"The (panel's top Democrat) Sander Levin and I together called for this hearing," Camp said. "This isn't a partisan hearing."
Levin, however, told CNN he's "always concerned these days that partisanship will take over."
"This should be an inquiry. We set it on a bipartisan path," Levin said. "I hope it stays that way."
Camp also promised more hearings to follow, partly to hear from former IRS Commissioner Doug Schulman, who was running the agency when the targeting program went into effect.
Should anyone involved in the scandal go to jail, as House Speaker John Boehner has suggested?
"I don't know that answer yet," Camp said. "But clearly this is serious. I think the penalties should be serious. I think Infringing on people's constitutional rights is not something we should look (at) as a trifling matter."
Separately, former IRS Commissioner Douglas Shulman, who was at the helm of the agency during most of the period in question, will testify before the House Oversight Committee next Wednesday, a House GOP aide told CNN.
Shulman -- no longer in the government -- agreed to attend voluntarily.
Another official at the heart of the scandal, Lois Lerner, has told the committee through an attorney that she is currently in Montreal, and it's unclear if she can make the hearing.
Lerner is the head of the IRS tax-exempt division.
CNN's Deirdre Walsh contributed to this report