Remington rifles are displayed during the NRA Annual Meeting & Exhibits at the Kay Bailey Hutchison Convention Center on May 5, 2018 in Dallas, Texas.

"The Remington bankruptcy financing commitment was in the works for some months and occurred before our current policy was in place," she said.

"There have been some suggestions recently in the press that Bank of America is not standing by the policy that was announced in April" to no longer finance such manufacturers, the bank's vice chairman, Anne Finucane, said in the letter on Thursday.

A letter on Thursday obtained by CNBC may have only strengthened the resolve of gun reform activists, who are now calling on people to boycott the bank based on its involvement in the Remington bankruptcy loan.

Bank of America is trying to clarify "confusion" about its bankruptcy loan to rifle maker Remington in light of the bank's statement in April that it would no longer finance makers of military-style guns for civilian use.

In a television interview in April, Finucane said it is no longer Bank of America's "intent to underwrite or finance military-style firearms on a go-forward basis." Finucane's remarks came more than a month after the mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, that left 17 students and adults dead.

News reports in May said the bank provided funding for Remington as part of a massive lending package, and gun reform activists cried foul.

Fred Guttenberg, the father of Jaime, 14, who was killed in the Florida school shooting, called for a boycott.

Guttenberg tweet

After reading Finucane's letter on Thursday, Guttenberg said his view had not changed at all.

Bank of America was "taking on Remington as a new customer," Guttenberg said, "at the same time they were telling us they were no longer doing anything like that." He had noted in a previous interview with CNBC that "the bankruptcy deal with Remington, it was only a couple weeks before Bank of America made their announcement. None of that happened in a vacuum."

The new letter "does not absolve them," he said. "Actually, it doesn't explain anything."

Guttenberg told CNBC that he and others connected to his movement and in Parkland are planning to close their Bank of America accounts en masse and set up elsewhere.

"Next week, we families here are going to make it very clear how we feel," Guttenberg said.

He added that "a bunch of students will be setting up their first bank accounts and it won't be at Bank of America."

David Hogg, a survivor of the shooting who has become a vocal gun-control activist, told CNBC in a text message Tuesday that he is "actively trying to change my bank account from Bank of America to another bank because of this."

In a second text message, Hogg said: "I am in full support of a boycott of Bank of America."

After reading the bank's Thursday letter, Hogg told CNBC that the bank "should invest in communities that are disproportionately affected by gun violence and intervention programs in those communities, such as Cure Violence or CeaseFire."

Any money the bank makes from the agreement with Remington should be donated to victims' funds for people affected by gun violence, Hogg added.

Cameron Kasky, another survivor of the Parkland massacre, told CNBC on Tuesday that Guttenberg "is a fantastic man who is dedicated to the gun reform movement and we're happy to stand beside him in his valiant efforts."

Kasky did not immediately respond to CNBC's requests for comment on the bank's most recent letter.