Kilroy Realty Corp. has commenced a secondary public offering of 4.5 million shares of common stock to raise money to acquire office buildings in Washington state.

After the markets closed on Tuesday, the Los Angeles real estate investment trust said it plans to use part of the net proceeds toward the $100 million purchase price of four office buildings in the Seattle suburb of Kirkland. Any remaining proceeds would be used to pay down an unsecured revolving credit facility, for other potential acquisitions or for general corporate purposes.

Kilroy will grant underwriters BofA Merrill Lynch, Barclays Capital and J.P. Morgan a 30-day option to purchase up to 675,000 additional shares to cover overallotments. At Tuesday’s closing price, the sale would result in gross proceeds of $204 million. The offering and overallotment would increase the number of shares outstanding, now at 52.3 million, by about 9 percent.

Shares, which closed up 7 cents, to $39.46 on the New York Stock Exchange, were down 4 percent in after-hours trading.